Systems, Methods, and Apparatus to Preheat Welding Wire

ABSTRACT

A contact tip assembly with a preheating tip comprises a welding-type power source configured to provide welding-type current to a welding-type circuit, the welding-type circuit comprising a welding-type electrode and a first contact tip of a welding torch; an electrode preheating circuit configured to provide preheating current through a first portion of the electrode via a second contact tip of the welding torch; and a preheat controller to: monitor a voltage drop across a second portion of the electrode; adjust at least one of the welding-type current or the preheating current based on the voltage drop, the second portion of the electrode comprising at least part of the first portion of the electrode; and control the preheating current based on a hydrogen reduction goal and based on stored parameters associated with a type of the electrode, a chemistry of the electrode, or a wire size.

RELATED APPLICATIONS

This patent arises from a continuation of U.S. patent application Ser.No. 15/498,249, filed Apr. 26, 2017, entitled “Systems, Methods, andApparatus to Preheat Welding Wire,” which is a continuation of U.S.patent application Ser. No. 15/343,992, filed Nov. 4, 2016, entitled“Systems, Methods, and Apparatus to Preheat Welding Wire” (now U.S. Pat.No. 10,675,699), which claims priority to U.S. Provisional PatentApplication Ser. No. 62/265,712 filed Dec. 10, 2015, entitled “WeldingTorch for Resistively Preheating Welding Wire,” and to U.S. ProvisionalPatent Application Ser. No. 62/329,378, filed Apr. 29, 2016, entitled“Welding Torch for Resistively Preheating Welding Wire.” The entiretiesof U.S. patent application Ser. No. 15/498,249, U.S. patent applicationSer. No. 15/343,992, U.S. Provisional Patent Application Ser. No.62/265,712, and U.S. Provisional Patent Application Ser. No. 62/329,378are incorporated herein by reference.

BACKGROUND

Welding is a process that has increasingly become ubiquitous in allindustries. Welding is, at its core, simply a way of bonding two piecesof metal. A wide range of welding systems and welding control regimeshave been implemented for various purposes. In continuous weldingoperations, metal inert gas (MIG) welding and submerged arc welding(SAW) techniques allow for formation of a continuing weld bead byfeeding welding wire shielded by inert gas from a welding torch. Suchwire feeding systems are available for other welding systems, such astungsten inert gas (TIG) welding. Electrical power is applied to thewelding wire and a circuit is completed through the workpiece to sustaina welding arc that melts the electrode wire and the workpiece to formthe desired weld.

While very effective in many applications, these welding techniques mayexperience different initial welding performance based upon whether theweld is started with the electrode “cold” or “hot.” In general, a coldelectrode start may be considered a start in which the electrode tip andadjacent metals are at or relatively near the ambient temperature. Hotelectrode starts, by contrast, are typically those in which theelectrode tip and adjacent metals are much more elevated, but below themelting point of the electrode wire. In some applications, it isbelieved that initiation of welding arcs and welds is facilitated whenthe electrode is hot. However, the current state of the art does notprovide regimes designed to ensure that the electrode is heated prior toinitiation of a welding operation.

Certain advancements have been made to the process of electrodepreheating. For example, U.S. Patent Publication No. 2014/0021183 A1 toPeters describes a welding torch having a contact tip that haselectrically isolated upper and lower portions, each portion providingpart of the aggregated welding current waveform. Similarly, U.S. Pat.Nos. 4,447,703, 4,547,654, and 4,667,083, as well as PCT Publication No.WO/2005/030422, describe various preheating techniques using a dualcontact tip. Despite the foregoing, a need remains for improved weldingstrategies that allow for welding initiation with a heated electrodewire so as to improve weld performance.

BRIEF SUMMARY

The invention relates to a wire preheating system, method, and apparatusfor use with a welding torch, more particularly, the invention relatesto a welding torch that enables continuously fed electrode wire to bepreheated for use in various forms of electric welding.

According to a first aspect, a welding system comprises: a contact tipassembly having a first contact tip portion and a second contact tipportion, wherein said first contact tip portion and said second contacttip portion are electrically isolated from each other (except throughthe electrode wire extending between the first and second contact tipportions) and each of said first contact tip portion and said secondcontact tip portion makes electrical contact with a same electrode wireduring a welding operation; a first power supply operably coupled tosaid first contact tip portion that provides a welding current to saidfirst contact tip portion during said welding operation; and a secondpower supply operably coupled to said second contact tip portion thatprovides a preheat current during said welding operation, wherein saidpreheat current enters said electrode wire at said second contact tipportion and exits at said first contact tip portion, and wherein saidwelding current enters said electrode wire at said first contact tipportion and exits via a welding arc at a weldment during said weldingoperation.

According to a second aspect, a contact tip assembly comprises: a firstcontact tip portion, wherein said first contact tip portion conducts awelding current provided by a first power supply during a weldingoperation; and a second contact tip portion, wherein said second contacttip portion conducts a preheat current provided by a second power supplyduring said welding operation, wherein said first contact tip portionand said second contact tip portion are electrically isolated from eachother (except through the electrode wire extending between the first andsecond contact tip portions) and each of said first contact tip portionand said second contact tip portion makes electrical contact with a sameelectrode wire during said welding operation, wherein said preheatcurrent enters said electrode wire at said second contact tip portionand exits at said first contact tip portion, and wherein said weldingcurrent enters said electrode wire at said first contact tip portion andexits via a welding arc at a weldment during said welding operation.

According to a third aspect, a method of welding comprises: conducting awelding current via a first contact tip portion provided by a firstpower supply during a welding operation; conducting a preheat currentvia a second contact tip portion provided by a second power supplyduring said welding operation; electrically isolating said first contacttip portion from said second contact tip portion; and establishingelectrical contact of said first contact tip portion and said secondcontact tip portion with a same electrode wire during said weldingoperation, wherein said preheat current enters said electrode wire atsaid second contact tip portion and exits at said first contact tipportion, and wherein said welding current enters said electrode wire atsaid first contact tip portion and exits via a welding arc at a weldmentduring said welding operation. In certain aspects, the method mayfurther comprise: determining a preheat temperature of a portion of theelectrode wire positioned between said first contact tip portion andsaid second contact tip portion, defining a determined preheattemperature; comparing the determined preheat temperature to a targetpredetermined preheat temperature; and prohibiting said first powersupply from providing said welding current to said first contact tipportion when the determined preheat temperature exceeds a predetermineddeviation from the target predetermined preheat temperature. In certainaspects, the method may further comprise: calculating a voltage dropacross said first contact tip portion and said second contact tipportion.

In certain aspects, the welding torch is a gooseneck welding torch.

In certain aspects, the welding torch is water cooled.

In certain aspects, the preheat current and welding current are suppliedby a common power source.

In certain aspects, the welding system calculates a voltage drop acrosssaid first contact tip portion and said second contact tip portion.

In certain aspects a dielectric guide is positioned between said firstcontact tip portion and said second contact tip portion.

In certain aspects, a temperature determining device determines apreheat temperature of a portion of the electrode wire positionedbetween said first contact tip portion and said second contact tipportion, defining a determined preheat temperature.

In certain aspects, the temperature determining device is a thermometer.

In certain aspects, the temperature determining device is a non-contactinfrared temperature sensor.

In certain aspects, the welding system compares the determined preheattemperature to a target predetermined preheat temperature and prohibitssaid first power supply from providing the welding current to the firstcontact tip portion when the determined preheat temperature exceeds apredetermined deviation from the target predetermined preheattemperature.

In certain aspects, the welding system compares a preheat voltage,indicative of a wire temperature, to a target predetermined preheatvoltage, indicative of a target temperature, and prevents the firstpower supply from providing the welding current to the first contact tipportion exceeding a predetermined current.

In certain aspects, the welding system has an upper current limit basedon a designated voltage, and may have multiple upper current limitscorresponding to different designated voltages. When the upper currentlimit is reached for a particular selected voltage, the welding systemshuts off the weld or limits the current to the upper current limit.

In certain aspects, a wire feeder is configured to drive the electrodewire forward to feed the electrode wire and in reverse to retract theelectrode wire.

In certain aspects, the wire feeder drives the electrode wire in reverseto retract the electrode wire such that the electrode wire's distal endis substantially at said first contact tip portion as part of an arcstarting algorithm.

In certain aspects, the wire feeder drives the electrode wire forward tofeed the electrode wire for a predetermined period of time after awelding arc is extinguished as part of an arc ending routine.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention will best be understood from adetailed description of the invention and a preferred embodiment thereofselected for the purposes of illustration and shown in the accompanyingdrawings in which:

FIG. 1 illustrates an example robotic welding system.

FIG. 2a illustrates a side view of an example robotic gooseneck weldingtorch with an air cooled preheater section.

FIG. 2b illustrates a cross sectional side view of an example roboticgooseneck welding torch with an air cooled preheater section.

FIG. 2c illustrates a perspective view of an example robotic gooseneckwelding torch with liquid cooled weld cables.

FIG. 2d illustrates a cross sectional perspective view of an examplerobotic gooseneck welding torch with liquid cooled weld cables.

FIG. 3 illustrates a functional diagram of an exemplary contact tipassembly.

FIG. 4 illustrates a flow chart of an example process for providing awelding current based upon the preheat temperature of an electrode wire.

FIG. 5 illustrates a flow chart of an example process for monitoring andadjusting the preheat temperature of an electrode wire.

FIG. 6a illustrates a timing diagram for an example weld startingsequence.

FIG. 6b illustrates a flow diagram of an example weld starting sequence.

FIG. 6c illustrates a timing diagram for another example weld startingsequence.

FIG. 6d illustrates a flow diagram of another example weld startingsequence.

FIG. 6e illustrates another example timing diagram of the example weldstarting sequence of FIG. 6 b.

FIG. 6f illustrates a flow diagram of another example weld startingsequence.

FIG. 7 illustrates a flow diagram of an example weld control scheme.

FIGS. 8a through 8d illustrate example pulsed preheat power suppliesthat can create a pattern of preheated hot spots on the wire.

FIGS. 9a through 9c illustrate a preheat torch various wireconfigurations.

FIGS. 10a and 10b illustrate deposition testing data.

FIG. 11 illustrates a functional diagram of another example contact tipassembly in which the power supply provides the welding power to theelectrode wire.

FIG. 12 illustrates a functional diagram of another example contact tipassembly in which the electrical connections between preheat powersupply and the contact tips are reversed relative to the connections inFIG. 11.

FIG. 13 illustrates a functional diagram of another example contact tipassembly in which the power supply provides the welding power to theelectrode wire.

FIG. 14 illustrates a functional diagram of another example contact tipassembly in which a single power supply that provides both preheatingpower and welding power to the electrode via the first contact tipand/or the second contact tip.

FIG. 15 is a flowchart illustrating an example method to use resistivepreheating to improve arc initiation for welding.

FIG. 16 illustrates an example welding assembly that uses a parabolicmirror as part of the gas nozzle to reflect arc light to preheat theelectrode wire extension.

FIG. 17 illustrates an example welding assembly that includes voltagesense leads to measure a voltage drop the two contact tips used forpreheating the electrode wire.

FIG. 18 illustrates an example welding assembly that includes anenthalpy measurement circuit.

FIG. 19 illustrates an example implementation of providing a resistivelypreheated wire to a workpiece and providing a separate arcing source,such as a tungsten electrode, to melt the wire.

FIG. 20 illustrates an example implementation of providing a resistivelypreheated wire to a workpiece and providing a separate arcing source,such as one or more laser source(s), to melt the wire.

FIG. 21 illustrates example wire preheat current and/or voltage commandwaveforms to reduce or prevent soft, preheated wire from beingcompressed and causing a jam between the first contact tip and thesecond contact tip.

FIG. 22 is a flowchart illustrating an example method to use resistivepreheating to improve arc initiation for welding.

FIG. 23 illustrates an example user interface device that may be used toimplement the user interface of the welding equipment.

FIGS. 24A, 24B, and 24C illustrate example average heat inputs fordifferent preheat levels.

FIG. 25 illustrates an example welding assembly that uses includes auser interface and a weld control circuit that implements a preheatcontrol loop.

FIG. 26 is a block diagram of an example implementation of the preheatcontrol loop of FIG. 25.

FIG. 27 is a block diagram of an example assembly to monitor hydrogenlevels in the electrode wire and preheat a section of the electrode wireto reduce hydrogen prior to welding.

FIG. 28 is a block diagram of an example implementation of the powersupplies of FIGS. 2, 11, 12, 13, 14, 17, 18, 25, and/or 27.

The figures are not to scale. Where appropriate, the same or similarreference numerals are used in the figures to refer to similar oridentical elements.

DETAILED DESCRIPTION

The present disclosure is directed to a system, method, and apparatusfor preheating wire electrodes. Preferred embodiments of the presentinvention are described herein with reference to the figures of theaccompanying drawings. Like reference numerals are used throughout thedrawings to depict like or similar elements. In the followingdescription, well-known functions or constructions are not described indetail, since such descriptions would obscure the invention inunnecessary detail.

For the purpose of promoting an understanding of the principles of theclaimed technology and presenting its currently understood, best mode ofoperation, reference will be now made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theclaimed technology is thereby intended, with such alterations andfurther modifications in the illustrated device and such furtherapplications of the principles of the claimed technology as illustratedtherein being contemplated as would typically occur to one skilled inthe art to which the claimed technology relates.

As used herein, the word “exemplary” means “serving as an example,instance, or illustration.” The embodiments described herein are notlimiting, but rather are exemplary only. It should be understood thatthe described embodiments are not necessarily to be construed aspreferred or advantageous over other embodiments. Moreover, the terms“embodiments of the invention,” “embodiments,” or “invention” do notrequire that all embodiments of the invention include the discussedfeature, advantage, or mode of operation.

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e. hardware) and any software and/orfirmware (code) that may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As usedherein, for example, a particular processor and memory may comprise afirst “circuit” when executing a first set of one or more lines of codeand may comprise a second “circuit” when executing a second set of oneor more lines of code. As utilized herein, “and/or” means any one ormore of the items in the list joined by “and/or”. As an example, “xand/or y” means any element of the three-element set {(x), (y), (x, y)}.In other words, “x and/or y” means “one or both of x and y.” As anotherexample, “x, y, and/or z” means any element of the seven-element set{(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, “x,y, and/or z” means “one or more of x, y and z”. As utilized herein, theterm “exemplary” means serving as a non-limiting example, instance, orillustration. As utilized herein, the terms “e.g.” and “for example” setoff lists of one or more non-limiting examples, instances, orillustrations. As utilized herein, circuitry is “operable” to perform afunction whenever the circuitry comprises the necessary hardware andcode (if any is necessary) to perform the function, regardless ofwhether performance of the function is disabled or not enabled (e.g., byan operator-configurable setting, factory trim, etc.).

As used herein, a wire-fed welding-type system refers to a systemcapable of performing welding (e.g., gas metal arc welding (GMAW), gastungsten arc welding (GTAW), etc.), brazing, cladding, hardfacing,and/or other processes, in which a filler metal is provided by a wirethat is fed to a work location, such as an arc or weld puddle.

As used herein, a welding-type power source refers to any device capableof, when power is applied thereto, supplying welding, cladding, plasmacutting, induction heating, laser (including laser welding and lasercladding), carbon arc cutting or gouging and/or resistive preheating,including but not limited to transformer-rectifiers, inverters,converters, resonant power supplies, quasi-resonant power supplies,switch-mode power supplies, etc., as well as control circuitry and otherancillary circuitry associated therewith.

As used herein, preheating refers to heating the electrode wire prior toa welding arc and/or deposition in the travel path of the electrodewire.

Disclosed wire fed welding-type systems include a welding-type powersource configured to provide welding-type current to a welding-typecircuit, the welding-type circuit comprising a welding-type electrodeand a first contact tip of a welding torch; an electrode preheatingcircuit configured to provide preheating current through a portion ofthe welding-type electrode via a second contact tip of the weldingtorch; and a voltage sense circuit to monitor a voltage at thewelding-type electrode and, based on the voltage, to determine a voltagedrop across the portion of the welding-type electrode, the electrodepreheating circuit to adjust the first current based on the voltagedrop.

In some examples, the electrode preheating circuit is configured toprovide the preheating current via the first contact tip, and theportion of the welding-type electrode is between the first and secondcontact tips of the welding torch. In some examples, the first contacttip is positioned closer to an arc end of the welding-type electrodethan the second contact tip. In some examples, the second contact tip ispositioned closer to an arc end of the welding-type electrode than thefirst contact tip. In some examples, the electrode preheating circuit isconfigured to provide the preheating current via a third contact tip ofthe welding torch. In some examples, the third contact tip contacts thewelding-type electrode such that the welding-type current and thepreheating current are superimposed on the portion of the welding-typeelectrode. In some examples, the third contact tip contacts thewelding-type electrode such that the welding-type current does not flowthrough the portion of the welding-type electrode that conducts thepreheating current.

In some example systems, the electrode preheating circuit is configuredto selectively subtract a portion of the welding-type current to reducepreheating of the portion of the welding-type electrode and selectivelyreduce the portion of the welding-type current being subtracted toincrease the preheating of the portion of the welding-type electrode.Some examples further include a stickout sense circuit to determine anelectrode stickout distance of the welding-type electrode, the electrodepreheating circuit to control the preheating current through the portionof the welding-type electrode based on the electrode stickout distance.In some examples, the stickout sense circuit comprises a welding-typecurrent sensor to measure the welding-type current, the stickout sensecircuit to determine the electrode stickout distance based on themeasurement of the welding-type current.

Some example systems further include an enthalpy measurement circuit todetermine an enthalpy applied to an electrode based on at least one of ameasured arc voltage, a measured welding-type current, or a measuredpreheating current, or the voltage drop across the portion of theelectrode, the electrode preheating circuit to control the preheatingcurrent based on the determined enthalpy and a target enthalpy to beapplied to the workpiece. Some examples further include a short circuitdetector to detect a short circuit condition at the welding-typeelectrode during a constant voltage mode, a pulse mode, and/or any otherwaveform mode of the welding-type power source. Some examples furtherinclude a power source controller to: when the short circuit detectordetects the short circuit condition, control the welding-type powersource to clear the short circuit condition using a constant currentmode; and when the short circuit detector detects that the short circuitcondition is cleared, control the welding-type power source to use theconstant voltage mode, the pulse mode, and/or any other waveform mode.Some examples further include a motor controller to: when the shortcircuit detector detects the short circuit condition, control a wirefeed motor to pause and/or retract the welding-type electrode; and whenthe short circuit detector detects that the short circuit condition iscleared, control the wire feed motor to advance the welding-typeelectrode.

Disclosed example methods include performing a welding operation in aspray transfer welding mode and reducing a current of the weldingoperation while accelerating a wire feed rate of the welding operationto cause wire to be fed into a weld puddle.

Disclosed example welding-type systems include a filler depositiondevice to heat a filler material and to deposit heated filler materialon a workpiece in one or more deposition passes without an electricalarc and a welding-type device to perform one or more passes on theworkpiece with the electrical arc. In some examples, the preheatingcircuit is switched off to increase (e.g., maximize) heat input for rootcapture in a root pass of a multi-pass welding operation, and switchedon to increase (e.g., maximize) deposition in fill and/or cap passes ofthe multi-pass welding operation.

Disclosed example welding-type systems include a welding-type powersource to provide welding-type power to an electrode wire at a weldingtorch; an electrode wire preheater to preheat the electrode wire; a wirefeed motor to feed the electrode wire to the electrode wire preheater; asensor to detect a short circuit event at the welding torch, wheresensor includes at least one of a motor torque sensor or an arc voltagesensor; and a preheat controller to control the electrode wire preheaterto slow and/or stop preheating the electrode wire in response todetecting the short circuit event, a stubbing event, a wire hang-upevent, and/or a feeding anomaly event at the welding torch. Some examplesystems further include a motor controller to cause the motor to retractthe electrode wire by at least a predetermined distance in response ashort circuit.

Disclosed example welding-type systems include a welding-type powersource to provide welding-type power to an electrode wire at a weldingtorch; an electrode wire preheater to preheat the electrode wire; apreheat monitor to monitor a preheating signal generated by theelectrode wire preheater and, based on the preheating signal, toidentify an anomaly in the preheating signal and/or arc signals based onat least one of a threshold signal level, a time derivative of thepreheating signal, an integral of the preheating signal, a statisticalanalysis of the preheating signal, or a stability over a time period ofthe preheating signal, the preheating signal comprising at least one ofa preheat voltage, a preheat current, a preheat power, a preheatenthalpy, or a preheat circuit impedance, the statistical analysiscomprising at least one of a mean of the preheating signal, a standarddeviation of the preheating signal, or a root mean squared value of thepreheating signal.

Disclosed example welding-type systems include a welding-type powersource to provide welding-type power to an electrode wire at a weldingtorch and an electrode wire preheater to preheat the electrode wire byradiating heat to the electrode wire. In some examples, the electrodewire preheater includes a wire liner for the electrode wire, theelectrode wire to travel through the wire liner toward the welding torchand a preheating power source to heat at least a portion of the wireliner, the at least the portion of the wire liner to preheat theelectrode wire at the electrode wire travels through the at least theportion of the wire liner.

Disclosed example welding-type systems include a welding-type powersource to provide welding-type power to an electrode wire at a weldingtorch to support an electrical arc and an electrode wire preheater topreheat the electrode wire by at least one of redirecting or focusinglight generated by the electrical arc toward the electrode wire.

Disclosed example welding-type systems include a welding-type powersource to provide welding-type power to an electrode wire at a weldingtorch and an electrode wire preheater to preheat the electrode wire. Theexample electrode wire preheater includes one or more infrared heatinglamps positioned within the welding torch.

Disclosed example welding-type systems include a welding-type powersource to provide welding-type power to an electrode wire at a weldingtorch; an electrode wire preheater to preheat the electrode wire; and aclamping diode to clamp a voltage between the electrode wire preheaterand the electrode wire to less than an arc initiation voltage.

Disclosed example welding-type systems include a welding-type powersource to provide welding-type power to an electrode wire at a weldingtorch, the welding-type power source to provide less than a thresholdcurrent to the electrode wire during a cladding operation; an electrodewire preheater to preheat the electrode wire near a melting point of theelectrode wire such that the current provided by the welding-type powersource is sufficient to melt the electrode wire; and a motor controllerto control a wire feed motor to oscillate the electrode wire, theoscillation of the electrode wire to cause melted portions of theelectrode wire to be ejected from the electrode wire toward a workpiece.The melted portions of the electrode wire are melted by the currentprovided by the welding-type power source.

Disclosed example welding-type systems include a welding-type powersource to provide at least one of welding-type power and preheatingpower to an electrode wire at a welding torch; a first circuit to directthe welding-type power to a first contact tip in the welding torch; asecond circuit to direct the welding-type power and the preheating powerto a second contact tip in the welding torch, where the first contacttip is closer than the second contact tip to a tip of the electrodewire; and a switching circuit. The switching circuit controls the firstcircuit to direct the welding-type power to the first contact tip priorto arc initiation while controlling the second circuit not to direct thewelding-type power and the preheating power to the second contact tipand controls the second circuit to direct the welding-type power and thepreheating power to the second contact tip after arc initiation whilecontrolling the first circuit not to direct the welding-type power tothe first contact tip.

Disclosed example welding-type systems include a welding-type powersource to provide welding-type power to an electrode wire at a submergedarc welding torch; an electrode wire preheating device to preheat theelectrode wire; and an electrode wire motor to move a tip of theelectrode wire within a deposition envelope of the submerged arc weldingtorch.

Disclosed example welding-type systems include an electrode wirepreheating device to preheat an electrode wire at a welding torch; awelding-type power source to provide welding-type power to the electrodewire at the welding torch; and a preheating controller to, in responseto detecting a trigger pull at the welding torch: cause the electrodewire preheating device to preheat the electrode wire at the weldingtorch; detect that the electrode wire has at least a threshold voltage;and enable the welding-type power source to provide the welding-typepower to the electrode wire to enable a start of a weld operation.

Some disclosed examples describe electric currents being conducted“from” and/or “to” locations in circuits and/or power supplies.Similarly, some disclosed examples describe “providing” electric currentvia one or more paths, which may include one or more conductive orpartially conductive elements. The terms “from,” “to,” and “providing,”as used to describe conduction of electric current, do not necessitatethe direction or polarity of the current. Instead, these electriccurrents may be conducted in either direction or have either polarityfor a given circuit, even if an example current polarity or direction isprovided or illustrated.

Referring to FIG. 1, an example welding system 100 is shown in which arobot 102 is used to weld a workpiece 106 using a welding tool 108, suchas the illustrated bent-neck (i.e., gooseneck design) welding torch (or,when under manual control, a handheld torch), to which power isdelivered by welding equipment 110 via conduit 118 and returned by wayof a ground conduit 120. The welding equipment 110 may comprise, interalia, one or more power sources (each generally referred to herein as a“power supply”), a source of a shield gas, a wire feeder, and otherdevices. Other devices may include, for example, water coolers, fumeextraction devices, one or more controllers, sensors, user interfaces,communication devices (wired and/or wireless), etc.

The welding system 100 of FIG. 1 may form a weld (e.g., at weld joint112) between two components in a weldment by any known electric weldingtechniques. Known electric welding techniques include, inter alia,shielded metal arc welding (SMAW), MIG, flux-cored arc welding (FCAW),TIG, laser welding, sub-arc welding (SAW), stud welding, friction stirwelding, and resistance welding. MIG, TIG, hot wire cladding, hot wireTIG, hot wire brazing, multiple arc applications, and SAW weldingtechniques, inter alia, may involve automated or semi-automated externalmetal filler (e.g., via a wire feeder). In multiple arc applications(e.g., open arc or sub-arc), the preheater may pre-heat the wire into apool with an arc between the wire and the pool. Optionally, in anyembodiment, the welding equipment 110 may be arc welding equipmenthaving one or more power supplies, and associated circuitry, thatprovides a direct current (DC), alternating current (AC), or acombination thereof to an electrode wire 114 of a welding tool (e.g.,welding tool 108). The welding tool 108 may be, for example, a TIGtorch, a MIG torch, or a flux cored torch (commonly called a MIG “gun”).The electrode wire 114 may be tubular-type electrode, a solid type wire,a flux-core wire, a seamless metal core wire, and/or any other type ofelectrode wire.

As will be discussed below, the welding tool 108 may employ a contacttip assembly 206 that heats the electrode wire 114 prior to forming awelding arc 320 using the electrode wire 114. Suitable electrode wire114 types includes, for example, tubular wire, metal cored wire,aluminum wire, solid gas metal arc welding (GMAW) wire, composite GMAWwire, gas-shielded FCAW wire, SAW wire, self-shielded wire, etc. In oneaspect, the electrode wire 114 may employ a combination of tubular wireand reverse polarity current, which increases the metal transferstability by changing it from globular transfer to a streaming spray. Bypreheating prior to wire exiting the first tip and fed in the arc (wherethe material transfer takes place), the tubular electrode wire 114 actsmore like a solid wire in that the material transfer is a more uniformspray or streaming spray. Moreover, there is a reduction in out-gassingevents and very fine spatter-causing events, which are normally seenwhile welding with metal core wire. Such a configuration enables thetubular wire to function in a manner similar to a solid wire typestreaming spray. Yet another benefit of preheating is alleviating wireflip due to poor wire cast and helix control in wire manufacturing(which may be more pronounced in tubular wire than solid wire) becausethe undesired wire twist will be reduced in the preheating section.

As will be discussed with regard to FIG. 2a through 2d , the weldingtool 108 may be a gooseneck torch, such as those used with roboticwelding, but other shapes are contemplated, including virtually any neckbend angle greater than zero, handheld versions for low hydrogen FCAWwelding, handhelds for GMAW, straight-neck hard automation torches,straight-neck SAW torches, etc. FIG. 2a illustrates a side view of anexample robotic gooseneck welding torch with an air cooled preheatersection. FIG. 2b illustrates a cross sectional side view of an examplerobotic gooseneck welding torch with an air cooled preheater section.FIG. 2c illustrates a perspective view of an example robotic gooseneckwelding torch with liquid cooled weld cables. FIG. 2d illustrates across sectional perspective view of an example robotic gooseneck weldingtorch with liquid cooled weld cables, where the copper conductorpartially shown. In certain aspects, a plurality of ceramic guides orrollers may be used to provide a preheater with a bend in it, whichmight have contact advantages with the contact tips and allow for uniqueform factors. In other aspects, the neck may be straight and the robotmounting bracket has the bend.

There are, however, a number of advantages to the gooseneck torchdesign. The gooseneck torch design, for example, allows for betteraccess to the weld joint 112, as well as automation capabilities inheavy equipment applications. The gooseneck torch design also allows forheavier deposition welding in tighter spaces compared to, for example, atandem torch design. Thus, in operation, the electrode wire 114 deliversthe welding current to the point of welding (e.g., the weld joint 112)on the workpiece 106 (e.g., a weldment) to form a welding arc 320.

In the welding system 100, the robot 102, which is operatively coupledto welding equipment 110 via conduit 118 and ground conduit 120,controls the location of the welding tool 108 and operation of theelectrode wire 114 (e.g., via a wire feeder) by manipulating the weldingtool 108 and triggering the starting and stopping of the current flow(whether a preheat current and/or welding current) to the electrode wire114 by sending, for example, a trigger signal to the welding equipment110. When welding current is flowing, a welding arc 320 is developedbetween the electrode wire 114 and the workpiece 106, which ultimatelyproduces a weldment. The conduit 118 and the electrode wire 114 thusdeliver welding current and voltage sufficient to create the electricwelding arc 320 between the electrode wire 114 and the workpiece 106. Atthe point of welding between the electrode wire 114 and the workpiece106, the welding arc 320 locally melts the workpiece 106 and electrodewire 114 supplied to the weld joint 112, thereby forming a weld joint112 when the metal cools.

In certain aspects, in lieu of a robot 102's robotic arm, a humanoperator may control the location and operation of the electrode wire114. For example, an operator wearing welding headwear and welding aworkpiece 106 using a handheld torch to which power is delivered bywelding equipment 110 via conduit 118. In operation, as with the system100 of FIG. 1, an electrode wire 114 delivers the current to the pointof welding on the workpiece 106 (e.g., a weldment). The operator,however, could control the location and operation of the electrode wire114 by manipulating the handheld torch and triggering the starting andstopping of the current flow via, for example, a trigger. A handheldtorch generally comprises a handle, a trigger, a conductor tube, anozzle at the distal end of the conductor tube, and, as disclosedherein, a contact tip assembly 206. Applying pressure to the trigger(i.e., actuating the trigger) initiates the welding process by sending atrigger signal to the welding equipment 110, whereby welding current isprovided, and the wire feeder is activated as needed (e.g., to drive theelectrode wire 114 forward to feed the electrode wire 114 and in reverseto retract the electrode wire 114). Commonly owned U.S. Pat. No.6,858,818 to Craig S. Knoener, for example, describes an example systemand method of controlling a wire feeder of a welding-type system. Thesubject disclosure may be practiced together with spin arc andreciprocating wire feed. In one example, the bottom tip may be moved tocause a preheated wire to spin. In another example, the wire may bemoved axially forward and backward prior to be pre-heated by reversewire feed motor upstream. Both spin and reverse wire feed on its own mayhave a positive effect in wire melt off rate and deposition. When theyare combined, the effect on deposition rate may be compounded.

FIG. 2A illustrates a perspective view of an example robotic gooseneckwelding torch 108. The illustrated gooseneck torch 108 generallyincludes a torch body 202, a gooseneck 204 extending from a forward endof the torch body 202, and a contact tip assembly 206 at a distal end ofthe gooseneck 204, or through the radius of the gooseneck 204. Theconduit 118 of the welding system 100 operably couples to a rear end ofthe torch body 202, which is further operably coupled to the robot 102and welding equipment 110. The conduit 118 supplies, inter alia,electrical current, shielding gas, and a consumable electrode (e.g.,electrode wire 114) to the torch body 202. The electrical current,shielding gas, and consumable electrode travel through the torch body202 to the gooseneck 204 and ultimately exit through an orifice at thedistal end of the contact tip assembly 206 where a welding arc 320 isultimately formed. In certain aspects, gooseneck torch 108 may be fluidcooled, such as air-cooled and/or liquid-cooled (e.g., water-cooled). Inone embodiment, the liquid cooling mechanism surrounds the preheatcontact tips and transfers away extra heat from the preheater inside thetorch body.

To facilitate maintenance, the gooseneck torch 108 may be configuredwith interchangeable parts and consumables. For example, the goosenecktorch 108 may include a quick change add on and/or a second contact tipthat allows adaptation of an existing water cooled/air cooled torch.Commonly owned U.S. Patent Publication No. 2010/0012637, for example,discloses a suitable gooseneck locking mechanism for a robotic torchhaving a torch body and a gooseneck that includes a connector receiverdisposed in the torch body.

The packaging of power source for pre-heat can take one of a variety offorms. In a preferred aspect, the pre-heat power supply may be integralwith the welding power supply, or inside the same housing. Inside thesame box, the pre-heat power supply can be an auxiliary power supplywith its own separate transformer feeding from the mains; however it isalso possible for the pre-heat power supply to share the same primaryand iron core of transformer for welding current by feeding off adedicated secondary winding. An integrated box provides simplicity ininter-connection, installation and service. Another embodiment is thatthe pre-heat power supply is separately packaged in its own housing withbenefit of retrofitting into existing installations and to permit a“mix-and-match” flexibility in pairing with other power sources, such asfor those suitable for open arc welding and sub-arc welding. Separatepackaging also requires communications between the controller inside thewelding power source and the preheating power source. Communication maybe provided through digital networking, or more specifically industrialserial bus, CANbus, or Ethernet/IP. Separate packaging may also resultin combining the power output of pre-heat power source and the output ofthe welding power source, possibly in the feeder, or in a junction boxbefore the torch, or in the torch itself.

In open arc welding, there are two derivatives, high deposition weldingcommonly seen in shipbuilding and heavy equipment fabrication (commonlygroove, butt and fillet joint, 15-40 ipm travel speed); and high speedwelding commonly seen in automotive (commonly lap joint, 70-120 ipmtravel speed). Pre-heat improves deposition and/or travel speed in bothcases. In open arc, GMAW with solid or metal core wire may be used; orFCAW with fluxed cored wire may be used as a process. In sub-arcwelding, solid or metal core wire may be used. In both open arc andsub-arc, multiple wire and/or arc combination is possible. For example,the lead wire has pre-heat and arc, but the trail wire has only pre-heatbut no arc. Another example is that both lead wire and trail wire haspreheat and arc. Yet another example is that there are 3 wires, wherethe first and third wire has both pre-heat and arc, but the middle wirehas preheat only but no arc. There are many permutations possible. Thethird group of applications is resistive preheating with anothernon-consumable heat source such as laser, plasma, or TIG, for welding,brazing, cladding, and hardfacing. The wire is pre-heated by resistivepreheat and fed into a liquid puddle melted by laser, plasma, or TIG.

In some examples, the second contact tip (e.g., further from the arc) isa spring loaded, one-size-fits-all contact tip. The spring pressure inthe second contact tip improves electrical contact despite electricalerosion and/or mechanical wear on the contact tip. Conventional springloaded contact tips are relatively expensive and are easily damaged byexposure to the arc and/or burn-back. However, using the spring loadedsecond contact tip that is not exposed to the arc and is not exposed toburn-back improves the longevity of the spring loaded contact tip.Because the torch accommodates different wire sizes, and a multi-size oruniversal second tip improves convenience to the weld operator byreducing the number of tips to be matched to the wire diameter, (e.g.,the first contact tip). The construction of the spring-loaded contacttip may be one piece (e.g., a tubular structure with slots so that thetines are adaptive to different wire diameter and apply pressure andreliable contact) or two or more pieces. For weld operators who areaccustomed to conventional guns and only having a single contact tip(e.g., the tip closer to the arc), the weld operator is rarely or neverrequired to replace the second contact tip, thereby improving the weldoperator experience using multiple contact tips.

FIG. 3 illustrates a functional diagram of an exemplary contact tipassembly 206, which may be used with welding system 100, whether roboticor manually operated. As illustrated, the contact tip assembly 206 maycomprise a first body portion 304, a gas shielding inlet 306, a firstcontact tip 318, a second body portion 310, a third body portion 312, aceramic guide 314, a gas nozzle 316, and a second contact tip 308. Whilethe first, second, and third body portions 304, 310, 312 are illustratedas separate components, one of skill in the art, having reviewed thepresent disclosure, would recognize that one or more of said bodyportions 304, 310, 312 may be fabricated as a single component. Incertain aspects, the contact tip assembly 206 may be added to anexisting welding torch. For example, the contact tip assembly 206 can beattached to a distal end of a standard welding setup and then used forresistive preheating. Similarly, the contact tip assembly 206 may beprovided as a PLC retrofit with custom software, thereby enablingintegration with existing systems that already have power sources andfeeders.

In some examples, the first contact tip 318 and/or the second contacttip 308 are modular and/or removable so as to be easily serviceable by auser of the welding system 100. For example, the first contact tip 318and/or the second contact tip 308 may be implemented as replaceablecartridges. In some examples, the welding equipment 110 monitorsidentifies one or more indicators that the first contact tip 318 and/orthe second contact tip 308 should be replaced, such as measurements ofthe used time of the first contact tip 318 and/or the second contact tip308, temperature(s) of the first contact tip 318 and/or the secondcontact tip 308, amperage in the first contact tip 318 and/or the secondcontact tip 308 and/or the wire, voltage between the first contact tip318 and/or the second contact tip 308 and/or the wire, enthalpy in thewire, and/or any other data.

In operation, the electrode wire 114 passes from the gooseneck 204through a first contact tip 318 and a second contact tip 308, betweenwhich a second power supply 302 b generates a preheat current to heatthe electrode wire 114. Specifically, the preheat current enters theelectrode wire 114 via the second contact tip 308 and exits via thefirst contact tip 318. At the first contact tip 318, a welding currentmay also enter the electrode wire 114. The welding current is generated,or otherwise provided by, a first power supply 302 a. The weldingcurrent exits the electrode wire 114 via the workpiece 106, which inturn generates the welding arc 320. That is, the electrode wire 114,when energized for welding via a welding current, carries a highelectrical potential. When the electrode wire 114 makes contact with atarget metal workpiece 106, an electrical circuit is completed and thewelding current flows through the electrode wire 114, across the metalwork piece(s) 106, and to ground. The welding current causes theelectrode wire 114 and the parent metal of the work piece(s) 106 incontact with the electrode wire 114 to melt, thereby joining the workpieces as the melt solidifies. By preheating the electrode wire 114, awelding arc 320 may be generated with drastically reduced arc energy.The preheat current can range from, for example, 75 A to 400 A, when thedistance between electrodes is 5.5 inches. Generally speaking, thepreheat current is proportional to the distance between the two contacttips and the electrode wire 114 size. That is, the smaller the distance,the more current needed. The preheat current may flow in eitherdirection between the electrodes.

To avoid unwanted kinking, buckling, or jamming of the electrode wire114, a guide 314 may be provided to guide the electrode wire 114 as ittravels from the second contact tip 308 to the first contact tip 318.The guide 314 may be fabricated from ceramic, a dielectric material, aglass-ceramic polycrystalline material, and/or another non-conductivematerial. The contact tip assembly 206 may further comprise a springloaded device, or equivalent device, that reduces wire kinking,buckling, and jamming, while increasing wire contact efficiency bykeeping the electrode wire 114 taught and/or straight.

In certain aspects, the second contact tip may be positioned at the wirefeeder (e.g., at welding equipment 110) or another extended distance, tointroduce the preheat current, in which case the preheat current mayexit a contact tip in the gooseneck torch 108. The contact tip in thegooseneck torch 108 may be the same, or different, from the contact tipwhere the welding current is introduced to the electrode wire 114. Thepreheat contact tip(s) may be further positioned along the electrodewire 114 to facilitate use with Push-Pull Guns, such as those availablefrom Miller Electric of Appleton, Wis. The liner could be made fromceramic rollers so the preheat current could be injected back at thefeeder and be a very low value due to the length of the liner.

The welding current is generated, or otherwise provided by, a firstpower supply 302 a, while the preheat current is generated, or otherwiseprovided by, a second power supply 302 b. The first power supply 302 aand the second power supply 302 b may ultimately share a common powersource (e.g., a common generator or line current connection), but thecurrent from the common power source is converted, inverted, and/orregulated to yield the two separate currents—the preheat current and thewelding current. For instance, the preheat operation may be facilitatedwith a single power source and associated converter circuitry. In whichcase, three leads may extend from the welding equipment 110 or anauxiliary power line in the welder, which could eliminate the need forthe second power supply 302 b.

In certain aspects, in lieu of a distinct contact tip assembly 206, thefirst contact tip 318 and a second contact tip 308 may be positioned oneach side of the gooseneck bend. For example, as illustrated by FIG. 2b, a preheat section may be curved (e.g., non-straight). That is, wire isfed through a section of the torch that has a bend greater than 0degrees or a neck that would be considered a “gooseneck”. The secondcontact tip 308 may be positioned before the initial bend and the firstcontact tip 318 after the bend is complete. Such an arrangement may addthe benefit to the connectivity of the heated wire moving through theportion of the neck between the two contact tips. Such an arrangementresults in a more reliable connection between the two contact tips wherean off axis, machined dielectric insert was previously needed.

The preheat current and welding current may be DC, AC, or a combinationthereof. For example, the welding current may be AC, while the preheatcurrent may be DC, or vice versa. Similarly, the welding current may beDC electrode negative (DCEN) or a variety of other power schemes. Incertain aspects, the welding current waveform may be further controlled,including constant voltage, constant current, and/or pulsed (e.g.,AccuPulse). In certain aspects, constant voltage and/or constant power,constant penetration, and/or constant enthalpy may be used to facilitatepreheat instead of constant current. For example, it may be desirable tocontrol the amount of penetration into the workpiece. In certainaspects, there may be variations in contact tip to work distances thatunder constant voltage weld processes will increase or decrease the weldcurrent in order to maintain a voltage at or close to the target voltagecommand, and thus changing the amount of penetration/heat input into theweld piece. By adjusting the amount of preheat current in response tochanges to contact tip to work changes the penetration/heat input can beadvantageously controlled. Furthermore, penetration can be changed toreflect a desired weld bead/penetration profile. For example, thepreheat current may be changed into a plurality of waveforms, such as,but not limited to, a pulse type waveform to achieve the desired weldbead/penetration profile.

The current could be line frequency AC delivered from a simpletransformer with primary phase control. Controlling the current andvoltage delivered to the preheat section may be simpler using a CC, CV,or constant power depending on how the control is implemented as well asthe power supply configuration to do it. In another aspect, the weldingpower source for consumable arc welding (GMAW and SAW) may includeregulating a constant welding current output and adapt wire speed tomaintain arc length or arc voltage set-point (e.g., CC+V processcontrol). In yet another aspect, the welding power source may includeregulating a constant welding voltage output (or arc length) and adaptwire speed to maintain arc current set-point (e.g., CV+C processcontrol). The CC+V and CV+C process controls allow for accommodation ofwire stick-out variation and pre-heat current/temperature variation byadapting wire feed speed (or variable deposition). In yet anotheraspect, the power source may include regulating a constant weldingcurrent output, the feeder maintains constant deposition, and thepre-heat power source adapts preheat current (or pre-heat power) tomaintain constant arc voltage (or arc length). It can be appreciatedthat the addition of pre-heat current/power adds a new degree of freedomto the wire welding processes (GMAW and SAW) that allows flexibility andcontrollability in maintaining constant weld penetration and weld width(arc current), deposition (wire speed) and process stability (arc lengthor voltage). These control schemes may be switched during the weldingprocess, for example, CV+C for arc start only, and other control schemesfor the main weld.

Using an advanced controlled welding waveform allows for the reductionin heat input, distortion, and improvements in bead geometry at highdeposition rates. Thus, expanding the operating range of pulse welding,reducing rotational transfer at high deposition rates, and reducingspatter caused by rotational spray. By preheating the electrode wire114, the operating range for pulse programs can be extended to higherdepositions. This is possible because of the lower power that is neededto transfer the material at those deposition rates. Before, the pulsewidth/frequency/peak amperage were too high at higher deposition rates,that the benefits of pulsing were no longer present. By preheating theelectrode wire 114, the operator is able to use similar pulse programsfor higher rates (e.g., 600 inches per minute (ipm)), which waspreviously only available at slower rates, such as 300 ipm. Preheatingthe electrode wire 114 also maximizes the benefit for pulse welding withlow background current. Furthermore, using a metal core with a custompulse configuration in combination with the contact tip assembly 206allows for heavier deposition welding at a higher quality. By preheatingthe electrode wire 114, it behaves similarly to a solid wire and itstransfer style.

Additionally or alternatively, preheating the electrode wire 114 enablesthe background current of the pulse waveform to be reducedsubstantially, as its primary function may be changed from growing aball to merely sustaining an arc between the electrode wire 114 and theworkpiece 106. Conventionally, the background current of the pulsewaveform is used to grow the droplet or ball, which is subsequentlydeposited to the workpiece 106. The example power supply 302 a mayimplement the pulse waveform based on the preheating power applied tothe electrode wire 114 by the preheat power supply 302 b.

The welding system 100 may be configured to monitor the exit temperatureof the electrode wire 114 between the preheat contact tips (e.g., thepreheat temperature), as illustrated, between the first contact tip 318and the second contact tip 308. The preheat temperature may be monitoredusing one or more temperature determining devices, such as athermometer, positioned adjacent the electrode wire 114, or otherwiseoperably positioned, to facilitate periodic or real-time weldingfeedback. Example thermometers may include both contact sensors andnon-contact sensors, such as non-contact infrared temperature sensors,thermistors, and/or thermocouples. An infrared thermometer determinestemperature from a portion of the thermal radiation emitted by theelectrode wire 114 to yield a measured preheat temperature. Thetemperature determining device may, in addition to or in lieu of thethermometers, comprise one or more sensors and/or algorithms thatcalculate the preheat temperature of the electrode wire 114. Forexample, the system may dynamically calculate temperature based on, forexample, a current or voltage. In certain aspects, the thermometer maymeasure the temperature of the dielectric guide or first contact tip toinfer the wire temperature.

In operation, the operator may set a target predetermined preheattemperature whereby the welding system 100 dynamically monitors thepreheat temperature of the electrode wire 114 and adjusts the preheatcurrent via the second power supply 102 b to compensate for anydeviation (or other difference) of the measured preheat temperature fromthe target predetermined preheat temperature. Similarly, controls may beset such that a welding operation cannot be performed until theelectrode wire 114 has been preheated to the predetermined preheattemperature.

FIG. 4 illustrates a flow chart 400 of an example process for providinga welding current based upon the preheat temperature of the electrodewire 114. The process starts at block 402 in response to, for example,activing the welding system 100 or receiving a trigger signal requestingthat the welding system 100 provide a welding current to the electrodewire 114.

At block 404, the welding system 100 receives a trigger signalrequesting that the welding system 100 supply a welding current to thewelding tool 108 (e.g., the electrode wire 114 via the first contact tip318). The trigger signal may be digital or analog and provided inresponse to an output from the robot 102 or actuation of a trigger by anoperator.

At block 406, the welding system 100 determines the preheat temperatureof the electrode wire 114 using one or more sensors and/or algorithms ofa temperature determining device, defining a determined preheattemperature. The determined preheat temperature may be a measuredpreheat temperature or a calculated preheat temperature. For example, asdiscussed with reference to FIG. 3, a thermometer may be positioned todetermine the temperature of the electrode wire 114 portion between thefirst contact tip 318 and the second contact tip 308. The welding system100 may also be configured to calculate the preheat temperature of theelectrode wire 114 using one or more devices and/or algorithms, therebyobviating the requirement for a thermometer (or provided in addition tothe thermometer). For example, the welding system 100 may employ aninternal loop to calculate the preheat temperature of the electrode wire114 based upon the preheat current, voltage, and/or power supplied tothe electrode wire, in addition to the heat generated by the resistiveheating at the stickout (e.g., the portion of electrode wire 114 thatextends beyond the contact tip where welding current is introduced, asillustrated, the first contact tip 318). If a thermometer is alsopresent, the measured preheat temperature may be compared to acalculated preheat temperature and optionally used to train thealgorithm.

The welding system 100 may determine the preheat temperature of theelectrode wire 114 at predetermine intervals (e.g., between about 1 and60 seconds, more preferably between about 1 and 10 seconds) ordynamically (e.g., in real-time). The welding system 100 may furtherstore the determined preheat temperatures to a database, therebyenabling the operators to track, view, and analyze the determinedpreheat temperature over a given period of time, which may prove usefulin identifying a potential cause of defect.

At block 408, the welding system 100 determines whether the determinedpreheat temperature falls within a predetermined operable range of atarget predetermined preheat temperature. That is, the predeterminedoperable range may permit a predetermined deviation from the targetpredetermined preheat temperature. For instance, if the predetermineddeviation is set to 10% and the target predetermined preheat temperaturemay be X degrees, the predetermined operable range would range from 0.9Xto 1.1X. While a predetermined deviation of 10% is provide as anexample, the predetermined deviation may be any deviation desired by theoperator and, therefore, should not be limited to 10%. In certainaspects, an alert may be provided to the operator if the determinedpreheat temperature is consistently on the high or the low end of thepredetermined operable range, indicating that adjustment may be needed.For example, an alert may be provided if the determined preheattemperature is on the high or the low end of the predetermined operablerange for a predetermined period of time (e.g., about 1 min to 60seconds, more preferably about 15 to 60 seconds). If the welding system100 determines that the determined preheat temperature falls within thepredetermined operable range of a target predetermined preheattemperature, the process proceeds to block 412. If the welding system100 determines that the determined preheat temperature falls outside ofthe predetermined operable range of a target predetermined preheattemperature, the process proceeds to block 410.

At block 410, the welding system 100 may adjust the preheat temperatureof the electrode wire 114. The preheat temperature may be adjusted byincreasing or decreasing the preheat current, power, and/or voltagesupplied by the welding system 100 to the portion of electrode wire 114to be preheated. An example process for monitoring and adjusting thepreheat temperature of the electrode wire 114 is described in greaterdetail with regard to FIG. 5.

At block 412, the welding system 100 supplies a welding current to thewelding tool 108 to facilitate a welding operation. The temperaturemonitoring loop, however, may be repeated until the trigger signal is nolonger received by returning to block 404.

A current pulse may be used to calculate any voltage drop across thefirst contact tip 318 and the second contact tip 308, a process that maybe integrated as part of a calibration routine. The welding system 100may be configured to account for the voltage drop across the contacttips (e.g., subtracting it out). For example, a one millisecond currentpulse (or energy pulse) may be used to gauge voltage drop. Further, thevoltage drop may be determined by measuring two pulses to isolatecontact resistance with wire resistance. This initial voltagemeasurement may be determined through both contact tips and a coldsection of welding wire, which establishes a constant contact resistanceand the resulting voltage drop across the contacts that can besubtracted out of the voltage drop across the preheat section measuredas the wire heats up. This then determines the resistive drop across theheated wire. Knowing the temperature coefficient of resistance of thewire, the average wire temperature can then be determined. Knowing thespeed of the wire and the power delivered to the wire, the peak wiretemperature can be determined.

FIG. 5 illustrates a flow chart 500 of an example process for monitoringand adjusting the preheat temperature of the electrode wire 114. Theprocess starts at block 502 in response to, for example, receiving asignal requesting that the welding system 100 provide a welding currentto the electrode wire 114.

At block 504, the welding system 100 determines the preheat temperatureof the electrode wire 114 using one or more sensors or algorithmssubstantially as discussed with regard to block 406 of FIG. 4.

At block 506, the welding system 100 determines whether the determinedpreheat temperature falls within a predetermined operable range of atarget predetermined preheat temperature substantially as discussed withregard to block 408 of FIG. 4. If the welding system 100 determines thatthe determined preheat temperature falls within the predeterminedoperable range of a target predetermined preheat temperature, theprocess returns to block 504, thereby effectively entering a loop. Ifthe welding system 100 determines that the determined preheattemperature falls outside of the predetermined operable range of atarget predetermined preheat temperature, the process proceeds to block508.

At block 508, the welding system 100 determines whether the determinedpreheat temperature is greater than the predetermined operable range.The predetermined operable range may include specified deviation(s) fromthe predetermined preheat temperature. If the welding system 100determines that the determined preheat temperature is greater than thepredetermined operable range, the process proceeds to block 512. If thewelding system 100 determines that the determined preheat temperature isnot greater than the predetermined operable range, the process proceedsto block 510.

At block 510, the welding system 100 determines whether the determinedpreheat temperature is less than the predetermined operable range. Ifthe welding system 100 determines that the determined preheattemperature is less than the predetermined operable range, the processproceeds to block 514. If the welding system 100 determines that thedetermined preheat temperature is not less than the predeterminedoperable range, the process proceeds to block 516 and optionally alertsto operator to a malfunction or error.

At block 512, the welding system 100 increases the preheat temperatureof the electrode wire 114. The preheat temperature may be increased byincreasing the preheat current, power, and/or voltage supplied by thewelding system 100 to the portion of electrode wire 114 to be preheated.The preheat current, power, and/or voltage may be increased atpredetermined intervals (i.e., X amps, X watts, X volts, etc.) until thepreheat temperature of the electrode wire 114 is determined to be withinthe predetermined operable range or at the target predetermined preheattemperature, which may be determined at block 504. Effectively, aninternal loop is established between blocks 504 and 508 until thepreheat temperature is found to be within predetermined deviation oftarget predetermined preheat temperature at block 506.

At block 514, the welding system 100 decreases the preheat temperatureof the electrode wire 114. The preheat temperature may be decreased bydecreasing the preheat current, power, and/or voltage supplied by thewelding system 100 to the portion of electrode wire 114 to be preheated.The preheat current, power, and/or voltage may be similarly decreased atpredetermined intervals (i.e., X amps, X watts, X volts, etc.) until thepreheat temperature of the electrode wire 114 is determined to be withinthe predetermined operable range or at the target predetermined preheattemperature, which may be determined at block 504. Effectively, aninternal loop is established between blocks 504 and 510 until thepreheat temperature is found to be within predetermined deviation oftarget predetermined preheat temperature at block 506.

At block 516, the welding system 100 ends the process. The process mayend as the result of, for example, an abort signal, error signal, ordiscontinuation of the welding operation (e.g., the welding system 100is shut off, put into idle mode, etc.).

Determining electrode stickout may also be used to make heatingadjustments to the electrode wire 114. To ensure that the distal end ofthe electrode wire 114 is heated to the predetermined preheattemperature, the welding system 100 may be configured with an arcstarting algorithm whereby the wire feeder draws the electrode wire 114in reverse such that the distal end of the electrode wire 114 issubstantially at the first contact tip 318, thereby heating the distalend of the electrode wire 114. This could be accomplished by monitoringthe voltage drop between the contact tips until the wire is retractedsuch that it does not make contact with the first contact tip. Then thewire can be slowly fed forward until contact is made. Preheating theelectrode wire 114 at the start, as well as with the other arc startingalgorithms disclosed herein, are beneficial in that they yield highquality arc starts and mitigate traditional arc starting shortfalls,such as wire batons, multiple hard-shorting events, lack offusion/penetration, etc., which can take place in non-preheated starts.

FIGS. 6a and 6b illustrate, respectively, a timing diagram 600 a and aflow diagram 600 b of example weld starting sequences, in other words, aroutine for synchronous wire heating and feeding prior to the start offorming the arc. When the trigger is actuated, a low level preheatcurrent is generated and directed to the electrode wire 114 to beginheating the electrode wire 114. When the electrode wire 114 reaches itsdesired run-in speed, the preheat is then increased to a higher preheatlevel to accommodate for the speed of the moving electrode wire 114. Asis understood by those of skill in the art, a run-in speed is the speedat which the electrode wire 114 is initially fed before it contacts theworkpiece. Generally speaking, run-in speed is slower than the wire feedspeed (WFS), which helps with arc starts and mitigates burnback. Once anarc is detected, the preheat current increases at a predetermined rate,which is commensurate with the WFS's ramp to a designated speed. Once atthe desired WFS, steady state heating takes place. For clarity, theincreased or decreased current occurs through the preheating powersource, not the welding power source. This starting routine may beperformed in combination with a contact tip to work distance predictionprocess. Once the welding equipment 110 has determined the currentcontact tip to work distance, the electrode wire 114 could be retractedsuch that the distal end of the electrode wire 114 is flush with the endof the contact tip. This would allow for full preheating of theelectrode stickout. This contact tip to work distance could be predictedduring pulse welding, or by pulsing quickly at the end of each weldcompleted in a CV-Spray transfer mode. Weld current feedback could alsobe used to determine contact tip to work distance changes. For example,the weld current could be compared to a known weld current thatcorresponds to one or more contact tip to work distances. The amount ofpreheat could then be increased or decreased based on the weld currentfeedback measured at the given wire feed speed. The voltage dropfeedback could be used for, inter alia, predictive maintenance (e.g.,contact tip wear), capturing welding anomalies, providing warnings tothe operator, generating initial electrode wire 114 temperatureestimations, and/or adjusting the configuration or algorithm of thewelding equipment 110. In certain aspects, the torch may be used forresistive preheating applications where there is no arc after thepreheated section. Further, handheld versions of the torch could be madefor burning off hydrogen in flux cored arc welding applications, as wellas other situations where ultra-low hydrogen would be desirable.Accordingly, a hydrogen sensor may be added to the torch to monitor theamounts of hydrogen being burnt off the electrode wire 114 or the amountthat is going into the weld.

With reference to FIG. 6b , an example weld starting process 600 b maybe initiated by actuating the trigger of the torch at block 602. Atblock 603, the welding equipment 110 determines whether the wire iscontacting both preheating contact tips. The wire may not be contactingboth preheating tips if, for example, the wire was changed. If the wireis contacting both preheating contact tips (block 603), at block 604,the welding equipment 110 may retract the electrode wire 114 apredetermined distance. If the wire is not contacting both preheatingcontact tips (block 603), at block 614 the welding equipment 110 feedsthe wire forward until contact is first detected.

If the welding equipment 110 detects a spike in the wire drive motorcurrent, the welding equipment 110 may stop retracting the electrodewire 114 at block 616, otherwise the process continues to block 608. Atblock 608, the welding equipment 110 determines whether a loss inconnectivity exists with regard to the first contact tip. If there is noloss in connectivity, the process returns to block 602. If there is aloss in connectivity, the process proceeds to block 610, where theelectrode wire 114 stops retracting. After stopping the wire retractingat block 610, or after feeding the wire forward at block 614, at block612 the welding equipment determines whether the wire is contacting bothpreheating contact tips. If the wire is not contacting both contact tips(block 612), control returns to block 614 to continue feeding the wireforward. By retracting and/or feeding the wire, the welding equipment110 may ensure that the distal end of the electrode wire 114 is at thefirst electrode (mitigating stickout). Once connectivity with the firstelectrode is reestablished, a low temperature preheat is applied atblock 618 to the electrode wire 114, which is stationary, between thetwo contact tips. At block 620, the welding equipment 110 begins drivingthe electrode wire 114 at run-in speed while feeding it with a preheatcurrent. At block 622, the welding equipment 110 detects initiation ofthe arc between the electrode wire 114 and weldment, after which thewelding equipment 110 reaches a steady state welding condition and WFS.The process may terminate at block 626 (e.g., upon releasing thetrigger).

In some examples, after beginning the low current preheat at block 612,the welding equipment 110 pauses the wire feed to permit the heatingeffects of the low current preheat to permeate the wire and reduce thelength of wire that is effectively cold (e.g., below a thresholdtemperature). In some examples, after beginning the low current preheatat block 612, the welding equipment repeats blocks 604, 606, 608 and610, at a slower feed forward speed (e.g., slower than a nominal run-inspeed) and a slow retract speed, so that the length of cold wireextending beyond the first contact tip is reduced (e.g., minimized). Thefirst iteration of blocks 604, 606, 608 and 610 can be done at higherspeeds, with the second iteration performed at a slower wire feed speedto improve precision. The pause in the wire feed can be quicker also tostop the wire feed before preheating the wire.

In the context of laser welding with resistive preheating (e.g., withoutan arc) and/or laser brazing with resistive preheating, reducing orminimizing the “cold wire” section and/or reducing or minimizing cycletime at the beginning of the process may be desirable. Cold wire refersto the un-preheated wire extending beyond the bottom (first) contacttip.

In some examples, blocks 604, 610 and 612 may be used to preset the wireextension prior to arc start. The sequence may be performed in betweenthe robot weld cycles or when the robot is not welding. By moving thewire back and forth and between the two tips to determine the exact wireend position, the welding equipment feeds the wire outside the bottomtip for a distance slightly below the contact-tip-to-work distance(CTWD) for arc start robot teach position ready for the next arc start.The actual wire run-in speed and run-in time (or cycle time) can bereduced (e.g., minimized) due to the short distance wire travel for arcstart.

FIG. 6c is a timing diagram 600 c illustrating another example routinefor synchronous wire heating and feeding prior to the start of formingthe arc. In the timing diagram 600 c, the wire does not advance until atarget wire preheat temperature and/or a wire preheat voltage indicativeof the wire preheat temperature is achieved. When the preheat target ismet, a preheat control loop (e.g., a voltage controlled weld controlloop (e.g., constant voltage) and/or a current controlled weld controlloop (e.g., constant current)) takes control of the preheat voltageand/or preheat current. When the preheat target is met, wire advancementbegins using a run-in wire speed.

With reference to FIG. 6d , an example weld starting process 600 dcorresponding to the timing diagram 600 c of FIG. 6c may be initiated byactuating the trigger of the torch at block 632. At block 634, thewelding equipment 110 performs a low temperature wire preheating. If thewelding equipment 110 detects that the target wire preheat temperatureand/or target preheat voltage is not reached at block 636, controlreturns to block 634. When the target wire preheat temperature and/orthe target preheat voltage is reached at block 636, the weldingequipment 110 beings a run-in wire feed at block 638. At block 640, thewelding equipment 110 beings control of the preheat current using avoltage controlled weld control loop (e.g., constant voltage) and/or acurrent controlled weld control loop (e.g., constant current). At block642, the welding equipment 110 detects initiation of the arc between theelectrode wire 114 and weldment. At block 644, the welding equipment 110reaches a steady state welding condition and WFS. The process mayterminate at block 646 (e.g., upon releasing the trigger).

FIG. 6e illustrates an example timing diagram 600 e of another exampleweld starting sequence. The timing diagram 600 e and weld startingsequence of FIG. 6e is similar to the timing diagram 600 a and startingsequence depicted in FIG. 6a , except that the timing diagram 600 eillustrates a loss of contact between the wire and the first contact tipwhile retracting the wire prior to preheating, and then advancement ofthe wire to reestablish contact between the wire and the first contacttip.

With reference to FIG. 6f , an example weld starting process 600 f maybe initiated by actuating the trigger of the torch at block 650. Atblock 652, the weld equipment 110 determines whether connectivitybetween the preheating contact tips is detected. If connectivity betweenthe preheating contact tips is detected (block 652), at block 654 thewelding equipment 110 retracts the wire at a first retraction speed(e.g., speed 1). At block 656, the welding equipment 110 determineswhether a threshold increase in the wire drive motor current is sensed.If a threshold increase in the wire drive motor current is not sensed(block 656), at block 658 the welding equipment determines whether aloss in connectivity between the preheating contact tips is sensed.While a loss in connectivity between the preheating contact tips is notsensed (block 658), control returns to block 654 to continue retractingthe wire. On the other hand, when a loss in connectivity between thepreheating contact tips is sensed (block 658), the welding equipment 110stops retracting the wire at block 660.

After stopping retraction of the wire (block 660), or if connectivitybetween the preheating contact tips is not detected (block 652), atblock 662 the welding equipment feeds the wire forward at a firstforward speed (e.g., speed 1). At block 664, the weld equipment 110determines whether connectivity between the preheating contact tips isdetected. If connectivity between the preheating contact tips is notdetected (block 664), control returns to block 662 to continue feedingthe wire.

When connectivity between the preheating contact tips is detected (block664), at block 666 the welding equipment retracts the wire at a secondretraction speed (e.g., slower than the first retraction speed). Atblock 668 the welding equipment determines whether a loss inconnectivity between the preheating contact tips is sensed. While a lossin connectivity between the preheating contact tips is not sensed (block668), control returns to block 664 to continue retracting the wire. Onthe other hand, when a loss in connectivity between the preheatingcontact tips is sensed (block 668), at block 670 the welding equipmentstops the wire retraction.

At block 672, the welding equipment feeds the wire forward at a secondfeed speed (e.g., slower than the first feed speed). At block 674, theweld equipment 110 determines whether connectivity between thepreheating contact tips is detected. If connectivity between thepreheating contact tips is not detected (block 674), control returns toblock 672 to continue feeding the wire.

When the welding equipment senses a threshold increase in the wire drivemotor current (e.g., at least a threshold increase in the wire drivemotor current) (block 656), at block 676, the welding equipment 110determines whether the current spike is an immediate or rapid spike. Forexample, an immediate or rapid spike may be identified if the currentincreases at higher than a threshold slew rate, and/or if the currentincreases above a threshold current in less than a threshold time. Ifthe current spike is an immediate or rapid spike (block 676), thewelding equipment identifies an error at block 690. The process mayterminate at block 692 (e.g., upon releasing the trigger or uponidentifying an error at block 690).

If the current increase is not an immediate or rapid spike (block 676),at block 678 the welding equipment 110 stops the wire retraction.

After stopping the wire retraction (block 678) and/or after detectingconnectivity between the contact tips (block 674), a low temperaturepreheat (e.g., low current preheat) is applied at block 680 to theelectrode wire 114, which is stationary, between the two contact tips.At block 682, the welding equipment 110 pauses the forward feeding ofthe wire 114 until a target parameter (e.g., temperature, voltage, etc.)is reached. At block 684, the welding equipment 110 begins driving theelectrode wire 114 at run-in speed while feeding it with a preheatcurrent. At block 686, the welding equipment 110 detects initiation ofthe arc between the electrode wire 114 and weldment, after which thewelding equipment 110 reaches a steady state welding condition and WFSat block 688.

FIG. 7 illustrates a flow diagram 700 of an example weld control scheme.The resistive preheat welding process is monitored as to allow for aconstant heat input process. In this process of welding, if something inthe path of the arc causes the welding current to exceed a predeterminedset current, the welding equipment 110 will adjust the preheat settingin order maintain the predetermined set current, thereby maintaining aconstant heat output from the welding arc. A similar process may be doneto account for a decreased welding current. The process may be adjustedfor a constant penetration mode, whereby the welding current could bemaintained while the preheat current is adjusted, allowing for aconstant penetration depth. In one aspect, a synergic mode may beemployed where the operator does not have to decide anything other thanthe ordinary welding parameters and the preheating condition would befully synergic and self-adjusting. In other example modes the end userhas some control of the preheating conditions taking place. Inoperation, the operator may set, for example, the desired preheatamount, the desired penetration level, the desired heat input level,etc.

With reference to FIG. 7, an example weld starting process 700 may beinitiated by actuating the trigger of the torch at block 702. At block704, the welding equipment 110 commences steady state welding (e.g.,block 624 of FIG. 6b ), which may occur after concluding startingsequence. At block 706, the welding equipment 110 welds withpredetermined preheat temperature, current, voltage, impedance, power,and/or enthalpy. For example, a predetermined preheat temperature of 800degrees Celsius. At block 708, the welding equipment 110 monitors weldcurrent feedback to maintain the predetermined preheat temperatureand/or current. If the weld current and/or voltage are too low, thewelding equipment 110 decreases the preheat current at block 712.Conversely, if the weld current and/or voltage are too high, the weldingequipment 110 increases the preheat current at block 710. The processcontinues until it is terminated upon, for example, releasing thetrigger.

The welding system 100 may be configured with an arc ending routine,which allows for the elimination of microwelds from the contact tip toelectrode wire 114. The ending routine may comprise one or more steps,including, for example, continuing wire movement, forward and/orreverse, after the welding arc 320 is extinguished. Thus, the wirefeeder drives the electrode wire forward and/or reverses to feed theelectrode wire for a predetermined period of time or predetermineddistance after the welding arc 320 is extinguished as part of the arcending routine. Additionally, the preheat current may also be rampeddown (i.e., decreased) at a slower rate to avoid fast solidificationinside the contact tip.

Creating preheating controls based off weld feedback and/or stickoutdistance, such as those used in the arc start and ending routines,reduces overall downtime that can result from over preheated wirefeeding and welding issues, as well as make the system easier for endusers to calibrate and use effectively.

Finally, the welding system 100 may be configured with an emergencyshutdown routine (or procedure). In an emergency shutdown routine,energy may be managed upon emergency power loss to avoid breakage of theelectrode wire 114 due to excessive preheating. For example, the preheatcurrent may be shut off, or dropped down to a predetermined emergencypreheat current value. Managing the arc outage routine (e.g., during,inter alia, an emergency shutdown routine) avoids electrode wire 114jams and microweld formations in the outermost contact tip, thusresulting in decreased overall down time of the welding system 100 and amore forgiving process in general (e.g., permitting for increasedeviation).

Referring to FIGS. 8a through 8d , the preheat power source 302 b may bea low cost capacitor discharge type and the preheat is provided as aheat pulse train, for the purpose of providing a series of hot spots inthe electrode wire 114 before it enters the contact tip 318. In anotherembodiment, the power source can be a switch-mode power supply capableof delivering a high narrow pulse (e.g. 1000 A for 1 ms). The purpose isto create a procession of preheated hot spots in the wire extension sothat hot spot reaches liquidus temperature before the wire section thatprecedes it. Chunks of solid wire may be detached at the hot spot. Thismay improve the melt off rate significantly at the same average weldingcurrent. In implementation, the stored energy in the capacitor maydischarge into a load with little circuit inductance, such as having thecapacitor positioned near two contact tips. The capacitor charge circuitcan be located away from the contact tip, such as, for example, packagedinside the wire feeder or main welding power supply with cables insidethe torch composite cable to complete the circuit to the preheat energystorage device. One implementation is having contact tips 308 and 318gapped 1 mm in between. This will create a very high but short currentpulse to superheat a band of wire e.g. 1 mm length just before it entersthe bottom tip, so the wire is fully supported to avoid buckle. Afterthe hot spot exits the bottom tip, it will be further heated byextension resistive joule heating and eventually accumulates enthalpyand reaches melting point while the wire ahead has not. In oneembodiment, the wire is fed at constant speed. In another embodiment,the wire feeding is momentarily stopped when the capacitor dischargetakes place to prevent wire melting from contact resistance at a slidingphysical contact with the contact tips 308 and 318.

The paragraphs below are related to using a capacitor discharge circuitto create an instantaneously high current spike, e.g. over 500 A,typically over 1,000 A or over 5000 A but very quick, e.g. less than 1millisecond, typically tens of microseconds. Referring to FIG. 6a , acapacitor bank is located very close to the torch body, possibly at rearend of the torch body itself so that the parasitic inductance to thecontact tips is minimized. The capacitor(s) are charged to hold energyby a charging circuit. A semiconductor switch, e.g. SCR, will dischargethe stored energy into the contact tips so that the wire between thetips are “super-heated” and creating a hot spot. As the pre-heated hotspots pass through the bottom tip and continue to be heated up by theextension joule heating, as they approach the arc. It is possible thathot spot closest to the arc can melt before the solid wire ahead of it,and the liquid is squeezed by Lorentz force of the welding current, and“chunk” of un-melted wire may fall off into the puddle. This willgreatly increase the deposition rate.

Referring to FIG. 8b . The power supply is connected to the bottom tipinstead of the top tip. This may minimize interference between thewelding circuit and the capacitor discharge circuit. Referring to FIG.8c , the preheat power source may be a DC, or AC supply with CV, CC, orconstant power output, essentially elevating the wire to approach apercent of but below the melting temperature. Referring to FIG. 8c andFIG. 8d , the capacitor discharge circuit serves as a pulse weldingpower supply but at a much higher peak current level to create a verylarge Lorentz force to squeeze the liquid at the end of the wireextension just before it reaches the arc. The timing of discharging thecap is important, ideally catching the liquid at the end of the wireextension during its down-swing (in oscillation). Referring to FIG. 8d ,it only needs one tip and both power supplies connect to the same tip.This may simplify the design. The welding power supply may be a constantcurrent, constant voltage or a DC pulse output. In case of pulse outputfrom the welding power supply, the capacitor discharge circuit dischargeat the end of the pulse. During the welding pulse, the liquid at the endof the wire extension is growing in size, so that the end of the weldpulse, a very high current peak is applied with large Lorentz force forliquid detachment. Another scenario is the welding pulse is a series ofsmall pulses, but the last pulse incorporates the capacitor dischargesuper pulse for detachment.

Again referring to FIGS. 8c and 8d , the capacitor discharge circuit mayfacilitate an arc start. During the arc start sequence, the preheatenergy storage capacitor(s) may be precharged and the switch is turnedon, as the wire is fed towards the workpiece at run-in speed. Upon firstcontact between the wire and the workpiece, the capacitor(s) maydischarge through the imperfect contact and its high contact resistance.The quick rise of current from the discharge results in a crisper andmore reliable arc start than that from demanding high current from thewelding power supply overcoming the weld cable inductance.

In another embodiment, the contact tip may be positioned before thegooseneck, while a high temperature, but electrically insulating liner,may be embedded inside the gooseneck for guiding the wire towards thefront end of the gun. This may create a very long wire extension(essentially the entire linear gooseneck length) for wire extensionheating, without the trouble of loss of gas shielding, wire flip etc.associated with conventional long extension welding. Yet anotherembodiment may be to use a copper shoe shaped interior of the gooseneckfor passing welding current, not on the single spot as in conventionalcontact tube (hole), but gradually over a sliding curved surface so thatthe welding current is passed from the copper shoe gradually over to thewelding wire (with infinite spots).

In some other examples, the second contact tip 308 is positioned insidethe wire feeder ahead of the power pin of the torch, which conductswelding current to the first contact tip 318 near the arc, so that thewire is preheated for the entire length of the welding torch between thefeeder and the first contact tip 318 at low preheat current. The wire isgradually warmed as the wire is conveyed from the feeder towards thefront of the torch.

As illustrated in FIGS. 9a through 9c , the preheat torch can be used incombination with a submerged arc power supply in a single preheatedwire, a tandem preheated wire (two power sources), and/or a twinpreheated wire configuration (one power source). For example, FIG. 9aillustrates a submerged arc (SAW) power supply in a single preheatedwire configuration. The wire may be preheated with CV AC, CV EP, CV EN,CV+C AC, CV+C EP, CV+C EN, CC AC, CC EP, CC EN, CC+V AC, CC+V EP, and/orCC+V EN. FIG. 9b illustrates a submerged arc power supply in a tandempreheated wire configuration. Wire could be used in a standard SAWconfiguration or any variation of the previously mentioned. The wire maybe preheated with CV AC, CV EP, CV EN, CV+C AC, CV+C EP, CV+C EN, CC AC,CC EP, CC EN, CC+V AC, CC+V EP, and/or CC+V EN. In certain aspects, 1wire may be preheated and one normal (Front-Back wires). Moreover,different polarity combinations may be employed for each wire (EP, EN,AC, CV+C, CC+V). One example tandem SAW configuration in FIG. 9b forcertain applications is that the lead arc is DCEP on unheated solid wirefor penetration, and the trail arc is DCEN on resistively preheatedmetal core wire for deposition. Finally, FIG. 9c illustrates a submergedarc power supply in a single preheated wire configuration. The wire maybe preheated with CV AC, CV EP, CV EN, CV+C AC, CV+C EP, CV+C EN, CC AC,CC EP, CC EN, CC+V AC, CC+V EP, and/or CC+V EN.

Results of testing in CV EP, EN, and AC are summarized in FIGS. 10a and10b . The results demonstrate a reduction in heat input and/or a gain indeposition of roughly 20-30% in most cases. The results also demonstratea reduction in penetration as the heat input decreased (shown in FIG.10a ). The results of the testing EP, EN, and AC in the CV+C mode showed20-25% gains in deposition as the wire feed speed was increased tomaintain a desired amperage. The penetration in this case was nearlyidentical to the non-preheated weld of the same amperage (i.e., FIG. 10b). Testing in all scenarios was done with both metal core and solidwelding wire. Weld tests also show that disclosed example resistivepreheating systems can produce the effect of heat inputreduction/deposition increase equivalent to an electrical stickout of 5inches or greater.

FIG. 11 illustrates a functional diagram of another example contact tipassembly 1100. The contact tip assembly 1100 is similar to the assembly206 illustrated in FIG. 3. The assembly 1100 includes the power supply302 a to provide the welding power to the electrode wire 114 (e.g., forgenerating the welding arc 320 or other welding power transfer). Theassembly 1100 also includes the power supply 302 b to generate a preheatcurrent to heat the electrode wire 114.

The assembly includes the first contact tip 318 and the second contacttip 308. The preheating power supply 302 b has the same electricalconnections to the second contact tip 308 and the first contact tip 318as described above with reference to FIG. 3. Instead of the weldingpower supply 302 a being electrically connected to the first contact tip318 (e.g., via the positive polarity connection) and the workpiece 106(e.g., via the negative polarity connection) illustrated in FIG. 3above, the welding power supply 302 a is electrically connected to thesecond contact tip 308 via the positive polarity connection and to theworkpiece 106 via the negative polarity connection.

In the example assembly of FIG. 11, the preheat power supply 302 bprovides preheating current to the portion of the electrode wire 114between the contact tips 308, 318, which may occur before welding and/orduring welding. In operation, the welding power supply 302 a providesthe welding current to support the arc 320. In the configuration of FIG.11, the energy provided by the welding power supply 302 a also preheatsthe electrode wire 114 between the second contact tip 308 and the arc320. In some examples, the preheat power supply 302 b provides power topreheat the electrode wire 114 in conjunction with the energy providedby the welding power supply 302 a, thereby reducing the power to bedelivered by the welding power supply 302 a.

FIG. 12 illustrates a functional diagram of another example contact tipassembly 1200. The assembly 1200 is similar to the assembly 1100 of FIG.11. However, the electrical connections between preheat power supply 302b and the contact tips 308, 318 are reversed relative to the connectionsin FIG. 11. In other words, the preheating power supply 302 b iselectrically connected to the second contact tip 308 via the negativepolarity connection and is electrically connected to the first contacttip 318 via the positive polarity connection.

In the example assembly 1200, the power supply 302 b may providepreheating power to the portion of the wire between the contact tips308, 318 while the welding power supply 302 a is not providing power(e.g., while not welding). When the welding power supply 302 a providesthe welding power to the assembly 1200, the preheat power supply 302 bis switched off and/or used to reduce a portion of the welding powerprovided by the welding power supply 302 a to control preheating of theelectrode wire 114 by the welding power supply 302 a.

FIG. 13 illustrates a functional diagram of another example contact tipassembly 1300. The assembly 1300 includes the power supply 302 a toprovide the welding power to the electrode wire 114 (e.g., forgenerating the welding arc 320 or other welding power transfer). Theassembly 1300 also includes the power supply 302 b to generate a preheatcurrent to heat the electrode wire 114. The welding power supply 302 ais electrically connected to the first contact tip 318 (e.g., via thepositive polarity connection) and the workpiece 106 (e.g., via thenegative polarity connection).

In the assembly 1300 of FIG. 13, the preheating power supply 302 b iselectrically connected to the electrode wire 114 such that the weldingcurrent provided by the power supply 302 a is not superimposed on thewire with the preheating current provided by the preheat power supply302 b. To this end, the example assembly 1300 includes a third contacttip 1302, to which the preheat power supply 302 b is electricallyconnected. While FIG. 13 illustrates an example in which the preheatingpower supply 302 b is electrically connected to the third contact tip1302 via the positive polarity connection and is electrically connectedto the second contact tip 308 via the negative polarity connection, inother examples the polarities of the connections are reversed.

FIG. 14 illustrates a functional diagram of another example contact tipassembly 1400. The assembly 1400 includes a single power supply thatprovides both preheating power and welding power to the electrode wire114 via the first contact tip 318 and/or the second contact tip 308. Tocontrol the direction of preheating and/or welding power to the contacttips 308, 318, the assembly 1400 includes a preheat/weld switch 1402.The preheat/weld switch 1402 switches the electrical connections betweenthe welding power supply 302 a and the first contact tip 318, the secondcontact tip 308, and/or the workpiece 106.

The welding power supply 302 a provides preheating to the electrode wire114 by, for example, controlling the preheat/weld switch 1402 to connectthe positive polarity terminal of the welding power supply 302 a to oneof the contact tips 308, 318 and to connect the negative polarityterminal of the welding power supply 302 a to the other of the contacttips 308, 318. The welding power supply 302 a provides welding to theelectrode wire 114 by, for example, controlling the preheat/weld switch1402 to connect the positive polarity terminal of the welding powersupply 302 a to one of the workpiece 106 or one of the contact tips 308,318 and to connect the negative polarity terminal of the welding powersupply 302 a to the other of the workpiece 106 or one of the contacttips 308, 318 (e.g., based on whether DCEN or DCEP is being used).

If the preheat/weld switch 1402 connects one of the terminals of thewelding power supply 302 a to the second contact tip 308 and connectsthe other of the terminals of the welding power supply 302 a to theworkpiece 106, the welding current supplied by the welding power supply302 a also provides preheating to the electrode wire 114. In someexamples, the preheat/weld switch 1402 alternates between connecting thewelding power supply 302 a to a first set of electrical connections forpreheating the electrode wire 114 (e.g., connecting to the contact tips308, 318), to a second set of electrical connections for welding (e.g.,connecting to the workpiece 106 and the first contact tip 318), and/orto a third set of electrical connections for simultaneously preheatingthe electrode wire 114 and welding (e.g., connecting to the workpiece106 and the second contact tip 308).

FIG. 15 is a flowchart illustrating an example method 1500 to useresistive preheating to improve arc initiation for welding. The method1500 may be used with any of the example assemblies 206, 1100, 1200,1300, 1400 of FIG. 2, 11, 12, 13, or 14. In general, the example method1500 preheats the electrode wire 114 and verifies that the electrodewire 114 it is at an elevated temperature before touching the workpieceto initiate an arc (e.g., via an operator, an automated system, etc.).When the electrode wire 114 has a higher temperature, arc initiation maybe easier because the initial contact resistance is typically higher.

The method 1500 starts at block 1502 in response to, for example,activing the welding system 100 or receiving a trigger signal requestingthat the welding system 100 provide a welding current to the electrodewire 114. At block 1504, the welding system 1000 determines a target arcstart voltage threshold (e.g., corresponding to a temperature to whichthe electrode wire 114 is to be preheated prior to an arc initiation).At block 1506, the welding system 100 applies preheat current to theelectrode wire 114 (e.g., via the welding power supply 302 a and/or thepreheat power supply 302 b).

At block 1508, the welding system 100 determines whether the electrodewire voltage is within a threshold deviation of the target arc startpreheat temperature. For example, the welding system 100 may measure orinfer the electrode wire temperature using a sensor and/or a thermalmodel. If the electrode wire temperature is not within a thresholddeviation of the target arc start voltage (block 1508), the method 1500returns to block 1506 to continue applying preheat current to theelectrode wire 114. Additionally, the method 1500 does not permit theadvancement of the wire. The wire voltage is indicative of a resistancein the wire, which is also indicative of the preheat temperature of thewire. When the electrode wire temperature is within a thresholddeviation of the target arc start voltage (block 1508), the system 100enables flow of welding current to the electrode wire 114 (e.g., enableswelding). At block 1512, the method 1500 ends.

Some examples involve using a preheated electrode wire to perform one ormore pre-weld passes to lay down filler material in a joint to be welded(e.g., to lay down metal in a joint first as “pre-deposit” without anarc). After the pre-deposit pass(es), examples include performing one ormore pass(es) with the arc (e.g., TIG and/or MIG), plasma, and/or laserto melt the pre-deposit material into the joint to perform the weld. Inother words, the pre-deposit material may be laid down like a hot andsoft “glue” with skin depth adherence to the workpiece, which may beperformed with or without weave patterns. The joint could be a squarejoint, a butt joint, a groove joint, a fillet joint, or any other typeof joint. The pre-deposit pass(es) and the welding pass(es) may bealternated, for multi-pass welding. Additionally or alternatively, thepre-deposit pass(es) and/or the welding pass(es) can have uneven numbers(e.g., lay down 2 pre-deposit pass then 1 weld pass). The pre-depositpasses can be performed using different weave patterns betweenpre-deposit passes (e.g., one pre-deposit pass on the left, one on theright, then a big weave of welding pass to melt both pre-depositpasses). The welding pass(es) may be performed with or without fillermetal. If the welding pass(es) are performed without filler metal (e.g.TIG, plasma, and/or laser), the pre-deposit and welding operations maybe done at different stations having a physical separation between thedeposition step and the weld step, which enables improved processcontrol, production flexibility, less distortion, and/or less base metaldilution. In some examples, the electrode wire that is resistivelypreheated by two adjacently positioned contact tips is used to depositpreheated filler metal directly into a melt pool on the workpiececreated by laser, electron beam or plasma arc.

In some examples, the electrode wire preheating methods and systemsdisclosed herein are used in combination with spin arc for submerged arcapplications to improve material deposition and/or weld speed.Additionally, spatter that is typically associated with spin arctechniques are contained under the flux used for submerged arc welding,enabling an improved weld bead appearance and adequate weld penetration.

FIG. 16 illustrates an example welding assembly 1600 that uses aparabolic mirror 1602 as part of the gas nozzle 316 to reflect arc lightto preheat the electrode wire 114 extension. The example parabolicmirror 1602 is configured to direct light generated by a welding arc 320to a small area of the electrode wire 114 near the welding arc 320. Inthe example of FIG. 16, the preheating power supply 302 b is omitted,but may be included to provide additional preheating when the weldingarc is not present.

In some examples, after the welding system 100 detects an end of the arcwelding process (e.g., release of the welding gun trigger) and after thearc power and the preheat power are stopped, the welding system 100controls a wire feed motor to retract the electrode wire 114 at least inthe amount of the distance between the two contact tips to cause thepreheated section of the electrode wire 114 to be retracted past thesecond contact tip 318. The retraction of the preheated and softenedportion of the electrode wire 114 makes it easier for an operator topull that portion of the wire out of a potential jam in the welding gun,rather than forcing the operator to move the wire by compression.

FIG. 17 illustrates an example welding assembly 1700 that includesvoltage sense leads 1702, 1704 to measure a voltage drop the two contacttips 308, 318 used for preheating the electrode wire 114. A preheatingmonitor 1706 monitors heating anomalies by comparing the measuredvoltages to threshold voltage level(s), by evaluating the timederivatives and/or integrals of the measured voltages, and/or bystatistical analysis (e.g., means, standard deviations,root-mean-squared (RMS) values, etc. Additionally or alternatively, thepreheating monitor 1706 monitors the stability of the voltage over alonger-term history (e.g. over minutes and/or hours). Additionally oralternatively, the preheating monitor 1706 monitors preheat current,preheat power, and/or preheat circuit impedance via the preheat powersupply 302 b.

Some example welding systems 100 use radiated heating to heat theelectrode wire 114 via a wire liner. An example includes constructingthe coiled wire liner using a nichrome alloy, platinum, and/or anothersuitable material, to simultaneously physically support and/or guide theelectrode wire 114 from the wire supply to the welding gun and to heatthe electrode wire 114 at the same time. The wire liner is heated by theexample preheat power supply 302 b. A shorter portion of the wire linermay be heated using higher heating current, and/or a longer portion ofthe wire liner (e.g., most of the wire liner extending from the wirefeeder to the welding torch) may be heated using a reduced heatingcurrent. The electrode wire 114 is gradually heated by the wire linerusing radiated heating so that the electrode wire 114 has an elevatedtemperature by the time the electrode wire 114 reaches the welding torchand/or the first contact tip 318.

Additionally or alternatively, the welding system 100 may use infraredheating lamps mounted within the gun body to preheat the electrode wire114. The infrared heating lamps are powered by the preheat power supply302 b.

Disclosed examples may be used to perform cladding operations withreduced dilution of the base material. In such examples, the preheatpower supply 302 b provides high preheat power to preheat wire to nearmelting. The welding power supply 302 a then provides a relatively lowarc current (e.g., 15-20 A) to bring the wire tip to the actual meltingpoint. However, because the relatively low current (e.g., 15-20 A) maynot be enough to cause pinching off of the melted wire to transfer theliquid metal across the arc, some such examples use a rapid-responsemotor to oscillate the wire. Oscillation of the wire jolts or shakes theliquid metal off of the wire tip. An example of such an oscillationtechnique is described by Y. Wu and R. Kovacevic, “Mechanically assisteddroplet transfer process in gas metal arc welding,” Proceedings of theInstitution of Mechanical Engineers Vol 216 Part B: J EngineeringManufacture, p. 555, 2002, which is incorporated by reference herein inits entirety. By using low arc current, the example cladding methodreduces base metal dilution and/or reduces costs of methods such aslaser cladding.

In some other examples, a cladding system uses resistive preheating ofthe electrode wire and a laser energy source to lay the cladding down.The laser beam may be defocused, and no welding arc (e.g., electricalarc) is present during the cladding operation. In some cases, thewelding arc is prevented via a voltage clamping system that clamps thevoltage between the wire and the workpiece to less than an arc strikingvoltage. Such a clamping system may include a diode and/or a transistor.

In some examples, welding-type equipment may be used to perform metaladditive manufacturing and/or additive metal coating. For example, acoating system or additive manufacturing system uses the wire preheatingand a voltage clamp as described above, but omits the laser. In someother examples, the cladding system uses the wire preheating and omitsboth the clamp and the laser. In either case, the metal may notnecessarily bond to the workpiece, but may form a coating and/or be laidon a base from which the metal can later be removed.

In some examples, a cladding system uses the resistive preheating topreheat the wire. The preheated wire is melted using a TIG welding arc.

Some example cladding systems use the preheating system to perform bothpilot preheating (e.g., prior to the wire making contact to theworkpiece where the two tips in the torch do the preheating) and atransferred preheating (e.g., open up the tip nearer the workpiece oncecurrent starts flowing in the work lead). The cladding system switchesthe preheating system between the pilot preheating mode and thetransferred preheating mode.

In some cases, preheating the electrode with an extended stick outlength can suffer from instability, which is caused by the short circuitcontrol response in submerged arc welding and/or in GMAW methods. Aconventional short circuit control response is to increase current toclear a detected short circuit. However, the current increase overheatsthe extended stick out to very high temperatures, causing the wire toloose rigidity and/or mechanical stability. As a result, the superheatedwire section melts off at a higher rate than normal and may introducearc length hunting or oscillation while the welding system 100 attemptsto obtain a stable arc length or contact tip to work distance. Someexamples address this instability by controlling the welding powersupply 302 a using a current-controlled (e.g., constant current) modeduring a prolonged short circuit event (e.g., a short circuit lastingmore than 5 ms). The current-controlled mode does not include a sharkfin response or high artificial inductance typical of short circuitclearing methods. For example, the current-controlled mode may use asame average current as used in the spray mode for that wire feed rate(e.g., a high current) or a fixed low current (e.g., 50 A or lower). Thewelding system 100 also initiates wire retraction to clear the shortcircuit. After the short is cleared, the welding system 100 reverts themode to voltage-controlled (e.g., constant voltage) spray and/or pulsespray mode. In such examples, the wire drive motor is highly responsive(e.g., similar to motors used in controlled short circuit (CSC) modes),but at reduced duty cycles relative to duty cycles used in CSC modes. Insuch examples, the motor is not used to clear shorts as quickly as inCSC modes.

Some examples increase the deposition rate of welding while reducingheat input to the workpiece using a spray mode. The welding system 100switches between spray mode at low wire speed mode and cold wire feed athigh wire speed mode. In this context, cold wire refers to non-meltedwire, whether preheated or not preheated. In some such examples, thewelding system 100 preheats the electrode wire 114 and performs weldingin a spray mode (e.g., voltage-controlled and/or pulse), and thenreduces the current to a lower current level (e.g., 50 A or less). Aftera period of operating in spray mode, the welding system and acceleratesthe wire feed rate (e.g., to the maximum motor feed rate) to input cold(e.g., non-melted) electrode wire 114 to the weld puddle. The input ofthe cold wire both adds filler metal and cools the weld puddle. Usingpreheated wire increases deposition of wire into the weld puddle beforethe weld puddle cools too much to further melt the wire, but preheatingof the wire may be omitted. The welding system 100 then retracts thewire while maintaining the lower welding current to restart the weldarc. When the arc is restarted, the welding system 100 returns to thespray mode at the higher current and feeds the electrode wire 114 at thelower wire feed rate. In some examples, the welding system 100 maintainsa higher current when feeding the cold wire into the weld puddle toincrease deposition, but reduces the current (e.g., to 50 A or less)prior to retracting the wire, to reduce spatter during the arc restart.In such examples, the wire drive motor is highly responsive (e.g.,similar to motors used in controlled short circuit (CSC) modes), but atreduced duty cycles relative to duty cycles used in CSC modes. In suchexamples, the motor is not used to clear shorts as quickly as in CSCmodes.

Poor physical contact between the electrode wire 114 and the contact tip318 can, in some cases, result in arcing between the electrode wire 114and the contact tip 318, which can damage the contact tip 318. Disclosedexamples include a clamping diode (e.g., a Zener diode) between to clampan output voltage of the preheat power source 302 b to clamp the outputvoltage to less than a threshold (e.g., less than 14V). Using theclamping diode reduces or eliminates the likelihood of initiating an arcbetween the contact tips 308, 318 and the electrode wire 114.Additionally, the clamping diode reduces the likelihood of arcing in thefirst contact tip 318 for the main welding current. When the physicalcontact is poor between the electrode wire 114 and the first contact tip318, the arc current flow may conduct or be redirected through theclamping circuit and the second contact tip 308 to the electrode wire114 to prevent tip burn back and extend the life of first contact tip318. The clamping diode is selected to have a current capacity toconduct both preheat current and welding current (e.g., with few hundrednanosecond turn-on). In some examples, the clamping diode is a siliconcarbide rectifier diode.

In some examples, the second contact tip 318 is used as a sensor fordetecting conditions for arcing at the first contact tip 308 (e.g.,without preheating the electrode wire 114). When such conditions forarcing at the first contact tip 308 are detected, the welding system 100clamps the tip-to-wire contact voltage as described above.

While examples disclosed above include contact tips 308, 318 that arecoaxially aligned, in other examples the axes of the contact tips 308,318 are offset (e.g., parallel but not aligned) and/or tilted (e.g., notparallel). In some other examples, a curved or bent wire support (e.g.,ceramic) is provided between the two contact tips 308, 318 to improvecontact at the first contact tip 308. In some other examples, the firstcontact tip 318 is provided with a spring-loaded contact to contact theelectrode wire 114, thereby ensuring contact between the first contacttip 318 and the electrode wire 114.

FIG. 18 illustrates an example welding assembly 1800 that includes anenthalpy measurement circuit 1802. The enthalpy measurement circuit 1802determines an enthalpy applied to the workpiece 106. The enthalpyapplied to the workpiece 106 by the power supplies 302 a, 302 b is a sumof the enthalpy introduced to the electrode wire 114 by the preheatpower source 302 b and the enthalpy introduced by the welding powersupply 302 a. The example measurement circuit 1802 may determine theenthalpy based on the measured arc voltage, the measured welding-typecurrent, and/or a measured preheating current, or the voltage dropacross the portion of the electrode. The electrode preheating circuit1802 controls the preheating current based on the determined enthalpyand a target enthalpy to be applied to the workpiece 106. For example,the electrode preheating circuit 1802 may reduce the preheating currentprovided by the preheat power supply 302 b based on welding powerapplied by the welding power supply 302 a to maintain a constantenthalpy applied to the workpiece 106. The welding power supply 302 amay provide a variable power based on, for example, changes in a contacttip to work distance and/or arc length.

In some examples, the welding system 100 includes a stickout sensecircuit that determines an electrode stickout distance of the electrodewire 114. The preheating power supply 302 b controls the preheatingcurrent based on the electrode stickout distance. An example stickoutsense circuit includes a current sensor to measure the welding currentsupplied by the welding power supply 302 a and determines the electrodestickout distance based on the measurement of the welding-type current.

FIG. 19 illustrates an example implementation of providing a resistivelypreheated wire 1902 to a workpiece 1904 and providing a separate arcingsource, such as a tungsten electrode 1906, to melt the wire 1902 and/orthe workpiece 1904. The wire 1902 is preheated using contact tips 1908and 1910, which are electrically coupled to a preheating power source1912. The example contact tips 1908, 1910 and the preheating powersource 1912, may be implemented as described with reference to any ofthe examples of FIGS. 3, 11, 12, 13, 17, and/or 18.

The tungsten electrode 1906 generates an electric arc 1914. A gas nozzle1916 is configured in a same torch as the tungsten electrode 1906 andprovides shielding gas 1918. A reciprocating wire feeder 1920 enablesbidirectional travel of the wire 1902 forward and/or in reverse. Thereciprocating preheated wire 1902 increases the welding or claddingtravel speed and, when using certain reciprocating frequencies, producesa grain refinement effect.

For welding, the example preheating power source 1912 preheats the wire1902 via the contact tips 1908, 1910, and the tungsten electrode 1906provides the additional heat required to melt the wire 1902 and/or aportion of the workpiece 1904 into a weld puddle 1922. The preheatedwire 1902 is melted after being submerged into the weld puddle 1922, ismelted by the arc 1914, and/or both. Any of the example controlprocesses described herein may be used to perform welding, brazing,cladding, hardfacing, metal addition, and/or any other welding-typeoperations.

FIG. 20 illustrates an example implementation of providing a resistivelypreheated wire 2002 to a workpiece 2004 and providing a separate arcingsource, such as one or more laser head(s) 2006, to melt the wire 2002.The example of FIG. 20 includes the contact tips 1908 and 1910, thepreheating power source 1912, and the reciprocating wire feeder 1920 ofFIG. 19. The example contact tips 1908, 1910 and the preheating powersource 1912, may be implemented as described with reference to any ofthe examples of FIGS. 3, 11, 12, 13, 17, and/or 18.

Similar to the tungsten electrode 1906 of FIG. 19, the laser head(s)2006 of FIG. 20 provide sufficient power to melt the workpiece 2004 toproduce the weld puddle 1922, into which the preheated wire 2002 issubmerged to melt the preheated wire 2002 for metal deposition. Use ofthe preheated wire 2002 involves applying less energy to the workpiece2004 via the laser head(s) 2006 than would be required when using a coldwire. In some cases the preheated wire 1902 gets melted after submergedinto the workpiece 1904 and/or the weld puddle 1922 without extra heatfrom the laser. In other cases, the laser adds more heat to the wire tobe melted into the melt pool 1922. The reduced laser power and heat helpreduce base metal dilution of the workpiece 1904 in a corrosionresistant weld overlay. As a result, the examples of FIGS. 19 and/or 20can achieve increased deposition rates over conventional cold wirewelding processes, with less likelihood of burning through theworkpieces 1904, 2004.

In some examples, the welding system 100 reacts to wire short circuitingevents. The example welding system 100 uses feedback to shut downpre-heat power immediately to prevent soft, preheated wire from beingcompressed and causing a jam between the first contact tip 318 and thesecond contact tip 308. The welding system 100 uses feedback such asfrom a wire feed motor (e.g., motor current, motor torque, etc.) and/oranother wire feed force sensor between the two tips motor current orother feeding force sensor to provide rapid detection. Additionally oralternatively, the welding system 100 uses feedback such as a durationof the short circuit measurement (e.g., arc voltage) to detect a wirestubbing event (e.g., extinguishing of the arc by contacting theelectrode wire 114 to the workpiece 106). In response to detecting theevent, the welding system 100 shuts down or disables the preheat powersupply to prevent wire noodling between the contact tips.

Additionally or alternatively, the welding system 100 may implement acontrolled preheat response to detecting wire short circuiting events.FIG. 21 illustrates example wire preheat current and/or voltage commandwaveforms 2102-2112 to reduce or prevent soft, preheated wire from beingcompressed and causing a jam between the first contact tip 318 and thesecond contact tip 308. In FIG. 21, weld voltage feedback 2114(represented by a waveform) is sensed by the welding system 100.

At a first time 2116, a wire stubbing event occurs, causing the weldvoltage feedback 2114 to decrease. In the illustrated example, thecontrol loop of the example system 100 does not identify a stubbingevent immediately upon the voltage drop. As a result, the examplewaveforms 2102-2108 do not respond to the initial drop at the first time2116. Conversely, the example waveforms 2110, 2112 respond to the sensedvoltage drop by decreasing the preheating command at a first rate.

At a second time 2118, the control loop in the welding system 100recognizes that the wire stubbing event has occurred. In response to thecontrol loop recognizing the wire stubbing event, the example waveforms2102, 2104 decrease to a reduced value, the waveforms 2106, 2108 beginramping down to a reduced value, and the waveforms 2110, 2112 decreasethe preheating command at a second rate higher than the first rate.

At a third time 2120, the wire stubbing event is cleared and the weldvoltage feedback 2114 increases to the nominal value. In response toclearing the wire stubbing event, the waveforms 2102, 2106, 2110increase to the nominal value substantially immediately. In contrast,the example waveforms 2104, 2108, 2112 ramp up to the nominal value.

While example waveforms 2102-2112 are illustrated in FIG. 21, any otherwaveforms may be used, including but not limited to combinations ofcomponents of the waveforms 2102-2112. Example waveforms may includevarying ramp rates that may be linear and/or non-linear.

FIG. 22 is a flowchart illustrating an example method 2200 to useresistive preheating to improve arc initiation for welding. The method2200 may be used with any of the example assemblies 206, 1100, 1200,1300, 1400, 1700, 1800 of FIG. 2, 11, 12, 13, 14, 17, or 18.

The method 2200 starts at block 2202 in response to, for example,activing the welding system 100 or receiving a trigger signal requestingthat the welding system 100 provide a welding current to the electrodewire 114. At block 2204, the welding system 100 enables the flow ofwelding current in the electrode wire 114 and enables feeding of thewire 114.

At block 2206, the welding system 100 begins the post-starting-sequencesteady state welding. At block 2208, the welding system welds with apredetermined preheat command target.

At block 2210, the welding system 100 determines (e.g., by measuring thetemperature of the electrode wire 114 via a sensor) whether theelectrode wire 114 preheat level is within a threshold deviation of thetarget preheat level (determined in block 2208). If the electrode wire114 preheat level is within a threshold deviation of the target preheatlevel (block 2210), control returns to block 2208 to continue welding.

If the electrode wire 114 preheat level is not within a thresholddeviation of the target preheat level (e.g., is too cold or too hot)(block 2210), at block 2212 the welding system 110 adjusts the preheatcurrent and returns control to block 2210 to check whether the preheatlevel is within the threshold deviation of the target preheat level.

In some examples, the welding equipment 110 includes or is incommunication with a user interface device to enable a user to adjustone or more preheat effects and/or parameters. FIG. 23 illustrates anexample user interface device 2300 that may be used to implement theuser interface of the welding equipment. The example user interface 2300may be implemented alone or as part of a larger welding user interfacethat permits control of other aspects of the welding equipment 110, suchas voltage, current, and/or wire feed speed setpoints, among otherthings.

The welding equipment 110 may use default voltage command(s), defaultcurrent command(s), default power command(s), and/or default enthalpycommand(s) to the preheating power source (e.g., the power sources 302a, 302 b) for corresponding wire speeds, joint thicknesses, and/or jointgeometry. However, such default commands may not always be theuser-desired amount for all situations. For example, the operator maydesire to change the command slightly to control the amount ofpenetration and/or heat input which, in turn, may mitigate welddistortion. The example user interface 2300 enables the user to finetune the preheat section of the weld condition to satisfy a particularapplication.

The example user interface 2300 includes a preheat adjustment device2302 and one or more preheat indicator devices 2304, 2306. In theexample of FIG. 23, the preheat adjustment device 2302 is a dial thatpermits the user to increase and/or decrease the preheat levelimplemented by the welding equipment 110 (e.g., by any of the exampleassemblies 206, 1100, 1200, 1300, 1400, 1700, 1800 of FIG. 2, 11, 12,13, 14, 17, or 18).

The graphic preheat indicator 2304 device graphically indicates to auser the preheat level 2308 selected via the preheat adjustment device2302, relative to a default preheat level 2310 and relative to apermitted range of the preheat level. The graphic preheat indicator 2304also includes identifiers indicating the effects of adjusting thepreheating level on weld penetration and/or other effects. For example,the graphic preheat indicator 2304 indicates that, as the preheat levelis increased, the weld penetration decreases and, conversely, the weldpenetration increases as the preheat level is decreased. As illustratedin FIGS. 24A, 24B, and 24C, the preheat level 2308 is graphicallyrepresented as shifting left and right as the graphic preheat indicator2304 is adjusted.

In the example of FIG. 23, the digital preheat indicator 2306 indicatesa numerical representation of the effect(s) on the weld of changing thepreheat level 2308 via the preheat adjustment device 2302. For example,the digital preheat indicator 2306 displays an average heat input to theweld based on the preheat level 2308. FIGS. 24A, 24B, and 24C illustrateexample average heat inputs for different preheat levels. Other examplenumerical representations include the voltage command, the preheatcurrent, the total energy of the system, and/or efficiency.

FIG. 25 illustrates an example welding assembly 2500 that uses includesa user interface 2502 and a weld control circuit 2504 that implements apreheat control loop 2506. FIG. 26 is a block diagram of an exampleimplementation of the preheat control loop 2506. The user interface 2502includes the user interface 2300 of FIG. 23 or another interface toenable a user of the welding assembly 2500 to adjust a preheat level.The weld control circuit 2504 receives a preheat level selected via theuser interface 2502 and controls the power supply 302 b to change thepreheat level. The weld control circuit 2504 may further control thepower supply 302 a to adjust one or more aspects of the welding powerbased on the preheat level selected to improve performance at theselected preheat level. The weld control circuit 2504 may also implementan electrode preheat control circuit.

The example preheat control loop 2506 of FIG. 26 automatically controlspreheat power 2602 to a weld process 2604 to maintain constantpenetration by using feedback from a penetration sensor 2606. An examplepenetration sensor uses weld current as a measure of weld penetration.Pulse voltage signature disruption by metal vapor pressure can be anadvance indication of burn-through. The example preheat control loop2506 uses the penetration sensor 2606 as close-loop feedback (e.g.,subtractive feedback from a desired penetration and/or preheat level2608 input from the user interface 2502). The preheat control loop 2506may improve poor penetration (e.g. partial penetration) and/or preventburn-through by detecting penetration and then using preheat power toadjust the penetration independently without introducing processinstability. Other example penetration sensors that may be used includeinfrared sensors external to the welding arc and the weld pool.

Returning to FIG. 25, the example assembly 2500 further includes voltagesense leads 2508, 2510 to measure a voltage across the preheated portionof the electrode wire 114. The voltage sense leads 2508, 2510 may becoupled, for example, to the two contact tips 308, 318, a wire liner, awire drive motor, a diffuser in the weld torch, and/or any othersubstantially electrically equivalent points). The weld control circuit2504 controls the preheat power supply 302 b using a preheat controlloop 2512. The preheat control loop 2512 uses the voltage sensed via theleads 2508, 2510 and the current output by the power supply 302 b tomaintain a commanded power input, current input, voltage input,enthalpy, and/or impedance to the section of the electrode wire 114. Inthe example of FIG. 25, the preheat control loop 2512 uses an errorbetween a commanded preheat voltage and the voltage sensed via the senseleads 2508, 2510 to adjust the preheat current, the preheat voltage,and/or the preheat power.

In some examples, the weld control circuit 2504 further receives weldvoltage feedback from the workpiece 106 and determines voltage dropsbetween the workpiece 106 and one or both of the contact tips 308, 318.The weld control circuit 2504 may calculate the total heat being inputto the electrode wire 114 and/or to the workpiece 106 by the powersupplies 302 a, 302 b using the voltage feedback including the contacttips 308, 318 and the workpiece 106, and/or control the voltages and/orcurrents output by the power supplies 302 a, 302 b.

A current present in a preheat circuit path (e.g., the power supply 302b, the contact tips 308, 318, and the section of the electrode wire 114between the contact tips 308, 318), and any other connecting circuitryand/or conductors) produces a voltage drop based on the amount ofcurrent and the amount of resistance in the circuit (e.g., in thesection of the electrode wire 114) where the voltage is being measured(e.g., via the voltage sense leads 2508, 2510). If a current is presentbut no voltage is measured, a conventional voltage controlled processwould increase the current command until the voltage error is zero(e.g., voltage error=voltage command−voltage feedback) and the commandis satisfied. Any loss of the voltage feedback (e.g., by disconnectionof either of the sense leads 2508, 2510, by short circuiting of thesense leads 2508, 2510, etc.) in a conventional voltage controlledprocess could cause the preheat current to increase high enough to meltor vaporize open the section of the electrode wire being preheated. Suchan event could result in a failure or destruction of a number of weldingtorch components.

The example weld control circuit 2504 detects and mitigates the loss ofvoltage feedback to the preheat control loop 2512 by reducing thecurrent command to the preheat power supply 302 b and/or turning off theoutput of the preheat power supply 302 b. For example, the weld controlcircuit 2504 may monitor the voltage and current in the preheat sectionof the electrode wire 114 to determine whether the voltage and currentare greater than respective thresholds (e.g., based on an expectedminimum voltage drop during preheating). If the threshold voltage andcurrent are not both present, the weld control circuit 2504 suspends ormodifies the preheat control loop 2512 to reduce the current command(e.g., to zero or to a predetermined safe level), cause the weldingpower supply 302 a to turn off welding power, and/or cause the preheatpower supply 302 b to turn off the preheat power. The weld controlcircuit 2504 may also indicate to the operator (e.g., via the userinterface 2502) that the sense lead connection has been lost (e.g., viadisplaying a message on a display device of the user interface 2502).The response to the loss of the preheat voltage feedback protects thetorch and the torch components (contact tip(s), gas nozzle, etc.), andreduces or prevents damage to the part being welded.

In some examples, the weld control circuit 2504 synchronizes thewelding-type current and the preheating current to reduce the netcurrent (and, thus, net heat) at the contact tips 308, 318. For example,the welding-type current and the preheating current may be alternatingcurrent, and the weld control circuit 2504 controls the preheatingcurrent and/or the welding-type current to be synchronous such thatcorresponding polarities of the welding type current and the preheatingcurrent result in reducing or canceling a net current at the contact tip318.

In some examples, the weld control circuit 2512 permits the weldingpower supply 302 a continue to provide welding power to weld withoutpreheating, but will weld at a higher weld current than when preheatingis enabled. The higher current could, depending on a number of factorssuch as wire speed, material thickness, and/or travel speed, causeexcessive penetration and/or damage the part being welded. The weldcontrol circuit 2504 may monitor the current from the welding powersource 302 a and be compared to a current limit (e.g., a current greaterthan the expected average current). If the current limit is exceeded,the weld control circuit 2504 turns off the weld power supply 302 a toavoid excessive penetration and/or workpiece damage.

As mentioned above, the user interface 2502 may output the heat input tothe workpiece 106 by the weld (e.g., based on the preheat level selectedvia the user interface 2502). The example weld control circuit 2504 ofFIG. 25 calculates the heat input based on the preheat voltage, preheatcurrent, preheat power, weld voltage, weld current, and/or weld poweroutput by the power supplies 302 a, 302 b. Due to heat losses betweenthe location in the assembly 2500 where the electrode wire 114 ispreheated and the location of the arc, the example weld control circuit2504 includes a loss factor in the heat input calculation. The exampleweld control circuit 2504 also includes an efficiency factor in thecalculation, where the efficiency factor compensates for inefficienciesin the power delivery to the electrode wire 114 and/or measurements ofthe voltage(s), current(s), and/or power(s) used to calculate the heatinput. The weld control circuit 2504 may calculate the heat input usingthe example Equation 1 below:

∫(αI_(weld)(t)*V_(weld)(t))dt  Equation 1

In Equation 1, a represents the efficiency and/or power losses in thewelding portion. The user interface 2502 may display the heat inputand/or the weld control circuit 2504 may use the calculated heat inputto control the preheat heat input and/or the weld heat input. The heatinput may be used in conjunction with, for example, penetration sensingto determine which of the preheating and/or welding power should beincreased and/or decreased to achieve a desired weld result.

As mentioned above, the example system 100 may preheat a section of theelectrode wire 114 to reduce the presence of hydrogen in the electrodewire 114 prior to welding. FIG. 27 is a block diagram of an exampleassembly 2700 to monitor hydrogen levels in the electrode wire 114 andpreheat a section of the electrode wire 114 to reduce hydrogen prior towelding. The assembly 2700 includes a hydrogen sensor 2702 and a preheatcontroller 2704. The preheat controller 2704 receives a hydrogenmeasurement signal from the hydrogen sensor 2702 and adjusts the preheatparameters (e.g., current, voltage, power, enthalpy, etc.) of thepreheat power supply 302 b and/or the welding parameters of the weldingpower supply 302 a.

By preheating the electrode wire 114 to a desired temperature at speedat which the electrode wire 114 is feeding out of the assembly 2700,relative to the amount of hydrogen present or allowable, the assembly2700 more easily reduces and/or eliminates excess hydrogen thanconventional methods of hydrogen reduction.

The preheat controller 2704 controls the preheat parameters, such aspreheat power, current, voltage and/or joule heating, based on observedbaking effectiveness for the type of electrode wire to reduce moisturein the type of electrode wire, and based on the feed speed of theelectrode wire 114. For instance, a higher feed rate of the electrodewire 114 may require higher preheat power. Welding with tubularelectrodes on butt joints may require less preheat power than tubularelectrodes with a joggle joint. Larger diameter tubular wire with morecross-sectional area may require higher preheat power. The examplepreheat controller 2704 may use a look-up table or other memorystructure to retrieve preheat parameters based on the type of tubularwire and wire feed rate input to the preheat controller 2704 (e.g., viaa user interface) or another input method. In such examples, the preheatcontroller 2704 may operate without the hydrogen sensor 2702 and rely onpredetermined preheat parameters.

The hydrogen sensor 2702 monitors the level of hydrogen on and/orproximate to the electrode wire 114. For example, the hydrogen sensor2702 may be a Palladium (Pd) based sensor such as aPalladium-functionalized carbon nanotube (CNT). Another exampleimplementation of the hydrogen sensor 2702 is as a diode-based Schottkeysensor with a Pd-alloy gate. Additionally or alternatively,highly-ordered vertically oriented titanium dioxide (TiO₂) nanotubemicroelectromechanical systems (MEMS) sensors may be incorporated in thewelding torch to detect low levels (e.g., in parts per million, partsper billion, etc.) of hydrogen in or proximate to the electrode wire114. The preheat controller 2704 performs closed-loop control of thepreheat power source 302 b based on the hydrogen measurement receivedfrom the hydrogen sensor 2702. The hydrogen sensor 2702 may also beplaced near a preheat chamber as a measure of hydrogen level beforedepositing the electrode wire 114 into the weld pool at the workpiece106 to form the weld metal. A moisture sensor may be used instead of oras a complement to the hydrogen sensor 2702.

The example assembly 2700 allows a tubular electrode to be produced atlow cost and yet achieve low hydrogen performance. The assembly 2700 mayalso reduce the cost of reducing or preventing hydrogen pick up duringproduction of the electrode wire 114, such as the costs associated withstrip steel quality, drawing lube, flux sourcing and storage, and/orother production, storage and/or procurement costs can be minimized.Furthermore, the cost of packaging and/or storage against moisture pickup in the electrode wire 114 can be reduced and the shelf life of theelectrode wire 114 can be extended.

Because hydrogen reduction is improved, a greater variety of tubularwires can be selected by fabricators for mechanical properties withhydrogen immunity provided by the example assembly providing wirepreheating at the weld torch. The reduction of hydrogen is made easierbecause it is not dependent on stickout length as in conventionaltechniques. End users cannot typically regulate stickout length in aconsistent manner, so performing hydrogen reduction via preheatingallows for a fixed, self-regulated preheat length so that the wireheating will be consistent and not reliant on stickout length. Theshorter stickout length also improves the CTWD and improves the responseto shorting and/or stubbing events by the welding power supply 302 a.The preheat hydrogen reduction method further eliminates the need topre-bake the electrode wire 114 for a significant period of time beforeusing the wire 114. The preheat hydrogen reduction method can heat theelectrode wire 114 more than possible when using a traditional extendedstickout method, further reducing hydrogen levels prior to introductionto the weld than conventional methods.

In some examples, the welding-type electrode is a tubular-typeelectrode, and diffusible hydrogen in the electrode is burned offsubstantially by preheating the electrode to prevent at least a portionof the hydrogen from being introduced into the weld metal. Thus,examples reduce the tendency of hydrogen induced cracking, stresscorrosion cracking, and hydrogen embrittlement in resulting welds.

FIG. 28 is a block diagram of an example implementation of the powersupplies 302 a, 302 b of FIGS. 2, 11, 12, 13, 14, 17, 18, 25, and/or 27.The example power supply 302 a, 302 b powers, controls, and suppliesconsumables to a welding application. In some examples, the power supply302 a, 302 b directly supplies input power to the welding torch 108. Inthe illustrated example, the welding power supply 302 a, 302 b isconfigured to supply power to welding operations and/or preheatingoperations. The example welding power supply 302 a, 302 b also providespower to a wire feeder to supply the electrode wire 114 to the weldingtorch 108 for various welding applications (e.g., GMAW welding, fluxcore arc welding (FCAW)).

The power supply 302 a, 302 b receives primary power 2808 (e.g., fromthe AC power grid, an engine/generator set, a battery, or other energygenerating or storage devices, or a combination thereof), conditions theprimary power, and provides an output power to one or more weldingdevices and/or preheating devices in accordance with demands of thesystem. The primary power 2808 may be supplied from an offsite location(e.g., the primary power may originate from the power grid). The weldingpower supply 302 a, 302 b includes a power converter 2810, which mayinclude transformers, rectifiers, switches, and so forth, capable ofconverting the AC input power to AC and/or DC output power as dictatedby the demands of the system (e.g., particular welding processes andregimes). The power converter 2810 converts input power (e.g., theprimary power 2808) to welding-type power based on a weld voltagesetpoint and outputs the welding-type power via a weld circuit.

In some examples, the power converter 2810 is configured to convert theprimary power 2808 to both welding-type power and auxiliary poweroutputs. However, in other examples, the power converter 2810 is adaptedto convert primary power only to a weld power output, and a separateauxiliary converter is provided to convert primary power to auxiliarypower. In some other examples, the power supply 302 a, 302 b receives aconverted auxiliary power output directly from a wall outlet. Anysuitable power conversion system or mechanism may be employed by thepower supply 302 a, 302 b to generate and supply both weld and auxiliarypower.

The power supply 302 a, 302 b includes a controller 2812 to control theoperation of the power supply 302 a, 302 b. The welding power supply 302a, 302 b also includes a user interface 2814. The controller 2812receives input from the user interface 2814, through which a user maychoose a process and/or input desired parameters (e.g., voltages,currents, particular pulsed or non-pulsed welding regimes, and soforth). The user interface 2814 may receive inputs using any inputdevice, such as via a keypad, keyboard, buttons, touch screen, voiceactivation system, wireless device, etc. Furthermore, the controller2812 controls operating parameters based on input by the user as well asbased on other current operating parameters. Specifically, the userinterface 2814 may include a display 2816 for presenting, showing, orindicating, information to an operator. The controller 2812 may alsoinclude interface circuitry for communicating data to other devices inthe system, such as the wire feeder. For example, in some situations,the power supply 302 a, 302 b wirelessly communicates with other weldingdevices within the welding system. Further, in some situations, thepower supply 302 a, 302 b communicates with other welding devices usinga wired connection, such as by using a network interface controller(NIC) to communicate data via a network (e.g., ETHERNET, 10baseT,10base100, etc.). In the example of FIG. 1, the controller 2812communicates with the wire feeder via the weld circuit via acommunications transceiver 2818.

The controller 2812 includes at least one controller or processor 2820that controls the operations of the welding power supply 2802. Thecontroller 2812 receives and processes multiple inputs associated withthe performance and demands of the system. The processor 2820 mayinclude one or more microprocessors, such as one or more“general-purpose” microprocessors, one or more special-purposemicroprocessors and/or ASICS, and/or any other type of processingdevice. For example, the processor 2820 may include one or more digitalsignal processors (DSPs).

The example controller 2812 includes one or more storage device(s) 2823and one or more memory device(s) 2824. The storage device(s) 2823 (e.g.,nonvolatile storage) may include ROM, flash memory, a hard drive, and/orany other suitable optical, magnetic, and/or solid-state storage medium,and/or a combination thereof. The storage device 2823 stores data (e.g.,data corresponding to a welding application), instructions (e.g.,software or firmware to perform welding processes), and/or any otherappropriate data. Examples of stored data for a welding applicationinclude an attitude (e.g., orientation) of a welding torch, a distancebetween the contact tip and a workpiece, a voltage, a current, weldingdevice settings, and so forth.

The memory device 2824 may include a volatile memory, such as randomaccess memory (RAM), and/or a nonvolatile memory, such as read-onlymemory (ROM). The memory device 2824 and/or the storage device(s) 2823may store a variety of information and may be used for various purposes.For example, the memory device 2824 and/or the storage device(s) 2823may store processor executable instructions 2825 (e.g., firmware orsoftware) for the processor 2820 to execute. In addition, one or morecontrol regimes for various welding processes, along with associatedsettings and parameters, may be stored in the storage device 2823 and/ormemory device 2824, along with code configured to provide a specificoutput (e.g., initiate wire feed, enable gas flow, capture weldingcurrent data, detect short circuit parameters, determine amount ofspatter) during operation.

In some examples, the welding power flows from the power converter 2810through a weld cable 2826. The example weld cable 2826 is attachable anddetachable from weld studs at each of the welding power supply 302 a,302 b (e.g., to enable ease of replacement of the weld cable 2826 incase of wear or damage). Furthermore, in some examples, welding data isprovided with the weld cable 2826 such that welding power and weld dataare provided and transmitted together over the weld cable 2826. Thecommunications transceiver 2818 is communicatively coupled to the weldcable 2826 to communicate (e.g., send/receive) data over the weld cable2826. The communications transceiver 2818 may be implemented based onvarious types of power line communications methods and techniques. Forexample, the communications transceiver 2818 may utilize IEEE standardP1901.2 to provide data communications over the weld cable 2826. In thismanner, the weld cable 2826 may be utilized to provide welding powerfrom the welding power supply 302 a, 302 b to the wire feeder and thewelding torch 108. Additionally or alternatively, the weld cable 2826may be used to transmit and/or receive data communications to/from thewire feeder and the welding torch 108. The communications transceiver2818 is communicatively coupled to the weld cable 2826, for example, viacable data couplers 2827, to characterize the weld cable 2826, asdescribed in more detail below. The cable data coupler 2827 may be, forexample, a voltage or current sensor.

In some examples, the power supply 302 a, 302 b includes or isimplemented in a wire feeder.

The example communications transceiver 2818 includes a receiver circuit2821 and a transmitter circuit 2822. Generally, the receiver circuit2821 receives data transmitted by the wire feeder via the weld cable2826 and the transmitter circuit 2822 transmits data to the wire feedervia the weld cable 2826. As described in more detail below, thecommunications transceiver 2818 enables remote configuration of thepower supply 302 a, 302 b from the location of the wire feeder and/orcompensation of weld voltages by the power supply 302 a, 302 b usingweld voltage feedback information transmitted by the wire feeder 104. Insome examples, the receiver circuit 2821 receives communication(s) viathe weld circuit while weld current is flowing through the weld circuit(e.g., during a welding-type operation) and/or after the weld currenthas stopped flowing through the weld circuit (e.g., after a welding-typeoperation). Examples of such communications include weld voltagefeedback information measured at a device that is remote from the powersupply 302 a, 302 b (e.g., the wire feeder) while the weld current isflowing through the weld circuit

Example implementations of the communications transceiver 2818 aredescribed in U.S. Pat. No. 9,012,807. The entirety of U.S. Pat. No.9,012,807 is incorporated herein by reference. However, otherimplementations of the communications transceiver 2818 may be used.

The example wire feeder 104 also includes a communications transceiver2819, which may be similar or identical in construction and/or functionas the communications transceiver 2818.

In some examples, a gas supply 2828 provides shielding gases, such asargon, helium, carbon dioxide, and so forth, depending upon the weldingapplication. The shielding gas flows to a valve 2830, which controls theflow of gas, and if desired, may be selected to allow for modulating orregulating the amount of gas supplied to a welding application. Thevalve 2830 may be opened, closed, or otherwise operated by thecontroller 2812 to enable, inhibit, or control gas flow (e.g., shieldinggas) through the valve 2830. Shielding gas exits the valve 2830 andflows through a cable 2832 (which in some implementations may bepackaged with the welding power output) to the wire feeder whichprovides the shielding gas to the welding application. In some examples,the welding system 302 a, 302 b does not include the gas supply 2828,the valve 2830, and/or the cable 2832.

While the present method and/or system has been described with referenceto certain implementations, it will be understood by those skilled inthe art that various changes may be made and equivalents may besubstituted without departing from the scope of the present methodand/or system. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the presentdisclosure without departing from its scope. For example, systems,blocks, and/or other components of disclosed examples may be combined,divided, re-arranged, and/or otherwise modified. Therefore, the presentmethod and/or system are not limited to the particular implementationsdisclosed. Instead, the present method and/or system will include allimplementations falling within the scope of the appended claims, bothliterally and under the doctrine of equivalents.

All documents cited herein, including journal articles or abstracts,published or corresponding U.S. or foreign patent applications, issuedor foreign patents, or any other documents are each entirelyincorporated by reference herein, including all data, tables, figures,and text presented in the cited documents.

1. (canceled)
 2. A consumable electrode-fed welding system, comprising:a welding power source configured to provide welding current to awelding circuit, the welding circuit comprising a welding electrode anda first contact point of a welding torch; and an electrode preheatingcircuit configured to supply preheating current through a first portionof the welding electrode to create a plurality of preheated regions inthe welding electrode.
 3. The consumable electrode-fed welding system asdefined in claim 2, wherein the welding power source is configured toprovide the welding current using a controlled waveform.
 4. Theconsumable electrode-fed welding system as defined in claim 2, whereinthe plurality of preheated regions in the welding electrode are spacedby cooler regions of the welding electrode.
 5. The consumableelectrode-fed welding system as defined in claim 4, wherein theelectrode preheating circuit and the welding power source are configuredto cause the preheated regions of the welding electrode to melt prior toa cooler region of the welding electrode that is closer to an arc formedby the welding current than the melted preheated region.
 6. Theconsumable electrode-fed welding system as defined in claim 2, whereinthe electrode preheating circuit is configured to create the pluralityof preheated regions in the welding electrode by generating increasedcurrent intervals and applying the increased current to the weldingelectrode.
 7. The consumable electrode-fed welding system as defined inclaim 6, wherein the electrode preheating circuit comprises a capacitorbank configured to generate the increased current intervals bydischarging the capacitor hank.
 8. The consumable electrode-fed weldingsystem as defined in claim 6, wherein the electrode preheating circuitis configured to generate the increased current intervals to be at least500 Amperes.
 9. The consumable electrode-fed welding system as definedin claim 6, wherein the electrode preheating circuit is configured toconduct the increased current intervals through the welding electrodevia the first contact point and a workpiece.
 10. The consumableelectrode-fed welding system as defined in claim 6, further comprising awire feeder configured to teed the welding electrode to the weldingtorch, wherein the wire feeder is configured to feed the weldingelectrode at a first feed rate during the increased current intervals tothe welding electrode and to feed the welding electrode at a second feedrate at times other than the increased current intervals.
 11. Theconsumable electrode-fed welding system as defined in claim 6, whereinthe electrode preheating circuit is configured to generate the increasedcurrent intervals as at least one of a current spike or a current pulse.12. The consumable electrode-fed welding system as defined in claim 2,wherein the electrode preheating circuit is configured to supply thepreheating current to the welding electrode via the first contact pointand a second contact point of the welding torch.
 13. The consumableelectrode-fed welding system as defined in claim 12, wherein the firstcontact point is positioned closer to an arc end of the weldingelectrode than the second contact point.
 14. The consumableelectrode-fed welding system as defined in claim 12, wherein the firstcontact point comprises a first contact tip and the second contact pointcomprises a second contact tip.
 15. The consumable electrode-fed weldingsystem as defined in claim 2, further comprising a wire feederconfigured to feed the welding electrode to the welding torch, whereinthe wire feeder is configured to feed the welding electrode at aconstant feed rate.
 16. The consumable electrode-fed welding system asdefined in claim 2, where the welding system is configured to perform atleast one of a gas metal arc welding process or a submerged arc weldingprocess.
 17. The consumable electrode-fed welding system as defined inclaim 2, wherein the electrode preheating circuit is configured tocontrol the preheating current based on a melting temperature of thewelding electrode.
 18. The consumable electrode-fed welding system asdefined in claim 2, further comprising a stickout sense circuit todetermine an electrode stickout distance of the welding electrode, theelectrode preheating circuit to control the preheating current throughthe first portion of the welding electrode based on the electrodestickout distance.
 19. The consumable electrode-fed welding system asdefined in claim 18, wherein the stickout sense circuit comprises awelding current sensor to measure the welding current, the stickoutsense circuit to determine the electrode stickout distance based on themeasurement of the welding current.
 19. The consumable electrode-fedwelding system as defined in claim 2, wherein the welding power supplyis configured to control a welding parameter associated with the weldingcurrent based on the preheating current.
 21. The consumableelectrode-fed welding system as defined in claim 2, wherein theelectrode preheating circuit is configured to control a preheatingparameter associated with the preheating current based on the weldingcurrent.
 22. The consumable electrode-fed welding system as defined inclaim 2, wherein the electrode preheating circuit is configured tosupply the preheating current to the welding electrode via a secondcontact point of the welding torch and a third contact point of thewelding torch.